3
PERSONAL SAFETY
CONTENTS of this section:
3.1
3.1.1
3.1.2
3.2
3.2.1
3.2.2
3.2.3
3.2.4
3.2.5
3.3
3.3.1
3.3.2
3.3.3
3.3.4
3.3.5
3.4
3.5
3.6
3.7
3.8
3.8.1
3.8.2
3.8.3
3.8.4
The legal framework
Duties of the employer and employee
Personal protective equipment (PPE)
Eye protection
The importance of eye protection
Safety considerations
Eye protection in practice
Maintenance
Repair
Other protective clothing
General
Laboratory coats
Gloves
Footwear
Respiratory protection
Hair
Eating and drinking
Hygiene
Lifting and transporting (Manual handling)
Safety screens
When to use
What to use
How to use
Making your own safety screens
3.1
The legal framework
3.1.1
Duties of the employer and employee
Page
301
301
301
302
302
302
304
309
311
312
312
312
313
314
314
315
315
315
315
318
318
320
320
322
Personal safety results from cooperation between employer and employee. Section
2.1.3 (Basic ideas behind health & safety law and its enforcement) explains that the
main responsibility to provide a healthy and safe working environment lies with the
employer; employees must, however, cooperate with the system the employer sets up,
following any instructions and guidance provided. They must also exercise a commonsense care for the health and safety of themselves and others. The section also explains that, while an employer must delegate health & safety functions to different
employees, this does not necessarily imply delegation of responsibility.
3.1.2
Personal protective equipment (PPE)
Regulations1 specifiy the employer’s duty to provide personal protective equipment for
employees (teachers and technicians). Where possible, PPE should be avoided; for
example, a proper ventilation system is preferred to personal respirators (gas masks).
However, in school labs, PPE such as eye protection and gloves will be needed.
The specific PPE Regulations do not cover pupils but the Health & Safety at Work Act
requires the employer to take care of them and the PPE Regulations will be considered
to provide appropriate guidance.
PPE must be adequate and appropriate for its intended use; an assessment of risks
must be made before any is provided. For example, eye protection must be suitable for
the activity it is to be used for and fit properly. It must be properly maintained.
1
Personal Protective Equipment at Work Regulations. See section 20.14.1 (Health & Safety at Work Act and its Regulations).
2004
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Employees cannot be required to pay for PPE. Thus an employee who normally wears
spectacles and who is required to wear eye protection for substantial periods can
request that the employer provides prescription safety spectacles. However, this does
not mean that extra money must be provided; the employee may be told to purchase
the spectacles out of the normal science budget and goggles or a face shield might be
provided instead.
3.2
Eye protection
3.2.1
The importance of eye protection
Eye protection should be worn whenever there is any recognised risk to the eyes.
Teachers should check any recommendations or instructions that their employer has
issued. Our own advice appears below.
3.2.2
Safety considerations
When eye protection should be worn1
Whether or not eye protection should be worn and the kind chosen must be considered
when making a risk assessment for an activity, with any employer’s instructions,
published advice and experience borne in mind.
Handling chemicals
m You should wear at least basic safety spectacles (to British/European Standard
BS EN 166, previously BS2092) whenever chemicals with a hazard classification are
handled. These should also be worn when using some chemicals that are sufficiently
dilute that they do not need to carry a hazard warning (eg, iodine solution, limewater
etc) but are nevertheless irritating to the eyes.
m Goggles which protect the eyes against chemical droplets/splashes (to BS EN 166 3) or
face shields marked BS EN 166 3 should be worn when handling:
•
•
all chemicals classified as CORROSIVE (eg, bromine, alkali solutions at
more than 0.5 M concentration, concentrated acids, solids such as
calcium oxide and phenol);
all chemicals classified as TOXIC.
[For classifications, see section 7.3.8 (Chemicals needing particular attention during
storage), section 7.4 (Handling and dispensing chemicals) and section 20.5 (Chemical
stocklist).]
m We recommend strongly that, in the following cases, face shields are worn in preference to goggles.
1
•
Dispensing large volumes of concentrated acids, alkalis or other corrosive chemicals.
•
Opening and dispensing from storage containers that may be under
pressure (‘880’ ammonia, hydrogen peroxide, silicon tetrachloride etc).
•
Handling molten alkalis.
Advice from National Interest Group for Education of the Health & Safety Executive
This is a quotation from Chapter 2 (2nd edition) or Chapter 5 (3rd edition) of Topics in Safety:
‘Spectacles are suitable for most operations.
A set of goggles should be available and worn where there is a particular risk. …
A face shield should be worn when large quantities of chemicals are dispensed, disposed of or cleared up after spillage.’
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m If any chemical splashes into the eye, this should be flushed immedi-
ately with running water. Hold the head over a sink and direct a
gentle but reasonably fast-flowing stream of water from a rubber
tube on a cold tap into the eye while holding the eyelids open.
Continue flushing for at least ten minutes and, for alkalis (unless
very dilute), until arrival at the hospital.
At least one tap in each laboratory should have a rubber tube about 300 mm long allocated to this purpose. There may be advantages in placing the piece of clean, soft
rubber tubing in a plastic bag, pinning it to the wall adjacent to the tap and clearly
labelling it FOR EMERGENCY EYE WASHING. The water company can require that the
tap concerned is connected to a storage tank, not directly to the mains. Such a tube is
also useful for rinsing spills elsewhere on the body.
m Sometimes, concerns are expressed about the quality of the water coming from tanks.
CLEAPSS has never heard of a problem when water from tanks has been used for
emergencies. However, if the water is clearly contaminated with particulate matter
then the only strategy may be to buy a sufficient quantity of sealed eye-wash bottles
filled with sterile water. At least two per laboratory will be required, together with a
reserve stock. Bottles usually have a limited shelf life and must then be replaced.
There is evidence from the small number of schools which use eye-wash bottles that
they forget to replace the bottles at appropriate intervals or are tempted, for financial
reasons, to keep them beyond their use-by date.
Hazards other than chemical
m Eye protection should be worn when there is a risk to the eyes from flying splinters
etc; hence eye protection at least to BS EN 166 should be worn for the following procedures (safety spectacles referred to above will normally be sufficient though, of
course, goggles or face shields will provide greater all-round protection).
•
•
•
•
•
•
m Hazards arising
from the use of
eye protection
Glass working
Breaking up rocks for geological studies
Stretching metal wires or plastic cords
Some dissection work
Metalwork or woodwork in the preparation room
Any other operation likely to give rise to flying splinters
What to do if a splash occurs to the upper part of the face depends on the type of
eye protection worn. If a solution is splashed on a child wearing chemical goggles
(see section 3.2.3), then the area should be washed before the goggles are removed.
However, if safety spectacles are worn, there is no protection at all from trickles of
solution which could run down the forehead into the eyes. Therefore, the spectacles
should be removed quickly before the area is washed.
Scratched eye protectors or goggles etc that have misted up can lead to risks of
accidents such as tripping or through the mishandling of imperfectly-seen apparatus. See section 3.2.4 for advice on avoiding these problems and section 3.2.5 for
removing scratches.
There have been reported incidents of the loose end of the elastic strap of goggles
flapping into a Bunsen burner flame and catching fire. It is therefore worth either
rethreading the elastic so that the loose ends are held between the main strap
and the head or sewing the ends of the elastic and using a small buckle for
adjustment (as used on bra straps). The latter solution is best when the available
elastic is thin and tends to pull out of the housing. Buckles are available from a
good haberdashery.
Personal safety
m Contact lens
wearers
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© CLEAPSS 2001
The wearing of contact lenses rather than spectacles is becoming more common.
Reports in the press of accidents in which contact lenses have contributed to an
injury, even though the reports have later been proved to be untrue, have led to
concern about the advisability of wearing lenses in school, particularly in laboratories and workshops.
Following discussions with safety experts and staff at Moorfields Eye Hospital, we
advise the following.
a) Pupils should be allowed to wear their contact lenses in science laboratories
as they appear to be at no greater risk than the pupils with no vision defects.
b) Pupils who normally wear contact lenses to correct vision defects should wear
eye protection over their lenses. The type of eye protection can usually be the
same as that used by the rest of the class.
c) Pupils and their parents should be warned that if an eye accident occurs,
contact lenses are likely to be lost down the sink during the essential first-aid
action of washing the eyes. Also, if the lenses are not lost, they should not be
worn again before consulting a medically qualified person, preferably an
opthalmologist, because of possible damage to the cornea. (This should be the
routine procedure following any such incident.) The lenses too should be
checked for contamination.
3.2.3
Eye protection in practice
Types of eye protection
European
Standard
EN 166
A more detailed discussion of the meaning of the European Standard and of the
types of eye protection available to schools, together with an evaluation of what is
on the market, is in CLEAPSS Guide R135, Eye and Face Protection.
The European Standard EN 166 was adopted in 1996 as the British Standard, BS
EN 166, replacing the former BS 2092. Existing eye protection to BS 2092 can
continue to be used but new purchases should conform to the new standard.
Understanding some parts of the standard is necessary to comprehend the
recommendations from your employer and the HSE.
Markings on the
frame
Markings on the
lens(es)
All eye protection which meets the requirements of the standard is marked on the
frame with:
• the manufacturer’s mark;
•
EN 166;
•
one or more code numbers to show the type of protection given (not on
spectacles),
•
a letter to represent the resistance to impact and,
•
optionally, a certification mark (eg, Kitemark).
Markings on the lens (ocular) show:
• the manufacturer’s mark;
•
a number to represent the optical class, and
•
a letter to represent the impact resistance (as on the frame).
Some other codings may also appear for specialist applications, but these are not
relevant to school science.
Types of
protection
m
Goggles and face shields (but not safety spectacles) may carry a number indicating
the type of protection they offer. Eye protection marked BS EN 166 3 guards
against liquid droplets and/or splashes. It is equivalent to BS 2092 C. Sometimes
goggles will also be marked with a 4 (protection against large dust particles
>5 µm) and a 9 (protection against splashes of molten metals and penetration of
hot solids).
For school science the code 3 is perfectly adequate but for foundry work in design
& technology the code 9 would be necessary and in dusty workshop environments
the code 4 may be needed. In practice, many goggles offer all three.
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In order to achieve chemical splash protection the vents must not allow fine
droplets through. Usually this means indirect ventilation. Unfortunately, in some
schools, pupils steal the vents, especially those with small metal gauzes that may
be used for drug abuse. Goggles with missing vents offer no better protection than
safety spectacles and must not be used if the risk assessment requires chemical
goggles. Not all goggles offer chemical splash protection, for example those with
direct vents shown in the second photograph below. Such goggles may well be
useful in workshops where impact resistance is important.
Goggles for
chemical splash
protection
BS EN 166 3
Goggles for
impact
protection only
BS EN 166
any eye protection of use in school science, the lenses should carry a letter
m Impact resistance For
indicating impact resistance. In order of increasing robustness, the letters are S
(no BS 2092 equivalent), F (equivalent to BS 2092 2), B (equivalent to BS 2092 1)
and A (only found on specialist face shields). Goggles would only have F or B. In
our view, BS EN 166 F is perfectly adequate for all the work likely to be carried
out in school laboratories or workshops.
Optical class
Lenses will carry a code 1, 2 or 3 to indicate optical quality. There was no BS 2092
equivalent. Code 1 represents the least distortion and is found on nearly all the
eye protection sold to the schools’ market.
Guidelines for provision of eye protection in science laboratories
For schools in which the policy is to ask parents to provide lab coats etc, it is sensible
to encourage them to provide eye protection too. The school would still need an
adequate stock of eye protection for use by visitors and pupils who have forgotten to
bring their own or who, for any reason, do not possess their own. As pupils may purchase unsuitable types of eye protection, arrangements would need to be made for
them to be purchased through the school, probably the same styles as the school stock.
Special arrangements may need to be made for senior science students who need to
wear eye protection for long periods of time.
The following points are summarised in Table 3.1 overleaf.
m Types
All eye protection should be marked EN 166. An ability to withstand low energy
impact, F, is probably a good idea, although prescription spectacles are only
tested to the lowest grade, S. If goggles are chosen, they should be marked EN
166 3 F.
m Appropriate
The temptation to provide eye protection of too high a standard should be resisted
because this may not be the best choice for school science laboratories. For
example, goggles marked EN 166 B 3459 would have no ventilation, would be
double glazed (and therefore very heavy) and the lenses would be made of polycarbonate which scratches easily. Such goggles are extremely uncomfortable.
standards
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m Pupils with special
Pupils with some types of special educational needs (SEN) may require different
educational needs types of eye protection from mainstream pupils. For example, those who are
visually impaired may need to work much closer to the apparatus and thus a face
shield may be appropriate. Similarly, those working in wheel chairs may be less
able to move out of the way in the event of a problem and those with motor
control difficulties may be more likely to have a splash accident. In both cases,
the higher protection afforded by face shields may be necessary.
m Safety spectacles
Safety spectacles cannot be grade 3 but should not be automatically ruled out on
that account. Because they are generally a comfortable form of eye protection,
they are more likely to be worn and are considered acceptable for some types of
school work with chemicals. See section 3.2.2.
m Face shields
Because the grading test for face shields depends on geometry and, in some
makes, the visor is further from the face than in others, some six-inch face
shields do not quite pass the test. Even so, we feel these offer good protection and
should not automatically be ruled out. This is particularly important for pupils
with small heads who have difficulty wearing other kinds of eye protection.
(Eight-inch face shields are too long for most pupils and some adults.)
A face shield
suitable for
school use
Table 3.1
Pros and cons of the different types of eye protection
Spectacles
Goggles
Face shields
Protection
Adequate for low risks
Needed for higher risks
Protects face as well as eyes
Cost
Moderate
Moderate
Initially expensive
Cleaning
Very easy
Washing and drying awkward
Easy
Comfort
High
Moderate
High but claustrophobic for some
Visibility
Good
Sideways vision often poor
Good all round
Lenses
Easily damaged
Housing gives some protection;
misting up a problem
Few problems
Over prescription specs
Problems
Often uncomfortable
Good
Storage
Reasonable
Reasonable
A problem
Other comments
Do not disrupt hairstyles
-
Muffle speech but give face
protection; may be especially useful
for some SEN pupils
Special requirements
m Laser goggles
These special (and very expensive) goggles are not required for the use of Class 2
lasers where the beam characteristics are such that they will not damage the eye,
ie, the beam is visible with a power less than 1 mW. In this case the only safety
precaution is the warning. Do not stare down the beam.
The laser classification used in this section comes from BS EN 60825. A different
definition of class 3A is used in the USA. If the laser is not marked clearly, it
must be considered hazardous.
Older lasers in schools may be unclassified or may be Class 3A or 3B because the
beam power exceeds 1 mW. Lasers in Class 3A have a beam which is too wide to
enter the human eye so that the fraction entering the pupil without an optical aid
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is less than 1 mW. Class 3B lasers are always dangerous and in this case teachers
demonstrating, and students using, lasers are advised to wear special protective
goggles. For Helium/Neon lasers used in schools, goggles should be made of BG18
Schott’s glass, 3 mm thick. Other types of glass are used for other lasers. Any
goggles, that reduce the intensity of laser light significantly, will make the beam
difficult to see and so less easy to direct safely. Wearing goggles is no substitute
for intelligent use of the laser. [See also section 12.12 (Lasers).]
Class 4 lasers should never be used in schools.
Workshops
This handbook is not written for those working in design and technology departments although some of the general comments on eye protection would be
relevant. The CLEAPSS publication Model risk assessments for design and technology in secondary schools gives advice on when eye protection is required for
different activities in design and technology.
Teachers may not be aware that prescription spectacles worn under goggles may
be a source of danger in workshops, if there is not a sufficient gap between the
spectacle lenses and the goggle lens to allow for its deformation during an impact.
Warnings about this are often included with new goggles and special doubleglazed models with a specified minimum gap are available.
Problems with eye protection
m Pupils take off the
eye protection
provided
Eye protection which is not being worn does not protect the eyes very well! The
HSE has accepted that a lower standard of protection, that is actually worn, may
be preferable to a higher standard that is not. Schools must have rules about
wearing eye protection and enforce them rigorously. There should be warnings
before an activity starts and reminders, as necessary, during the activity. There is
clear evidence that many incidents occur when pupils are clearing up at the end of
practical work, or when some are writing it up whilst others are continuing.
Therefore, if eye protection is required for a practical activity, all pupils must
continue to wear it whilst clearing up afterwards and when writing up (unless the
latter can be done at tables remote from the practical work). Teachers should
anticipate that pupils may remove eye protection after they have finished the
practical work and issue reminders as necessary. Teachers (and other adult
visitors to a practical lesson) should set a good example themselves.
Eye protection that is maintained in a good condition is more likely to be worn
than that which is badly scratched.
m Prescription
Prescription spectacles give less protection than safety spectacles conforming to
BS EN 166 and much less protection than goggles conforming to BS EN 166 3. If
the risk assessment requires goggles, then these must be worn over prescription
spectacles. Some types are better than others. Suitability is evaluated in our
guide R135, Eye and face protection. If the risk assessment requires safety spectacles then, ideally, these should be worn over prescription spectacles. Again, see
R135 for suitable models although it may be easier to provide goggles. The design
of some types of prescription spectacles gives better protection than that provided
by others. In relatively low risk situations it may be possible to rely on some types
of prescription spectacles alone but not, for example, when heating test tubes of
liquid where there might be a risk of the contents spurting out. A risk assessment
should be carried out, in addition to that on the relevant Hazcard, taking into
account the activity and the type of spectacles worn.
Small heads
Most of the eye protectors that are available are designed for use by adults in
industry and many are too large for most pupils and some staff in a school.
However, in recent years some manufacturers have started to cater for smaller
heads. Advice on particular models is given in our guide R135, Eye and face protection, but general comments are given here.
spectacles
Investigations in schools have shown that there is a significant number of pupils
aged 11-12 years with very small heads. Most safety spectacles fall off these
pupils, particularly if they look slightly downwards, as they would do when writing notes. The best thing to do if this happens is to drill holes in the ends of the
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side arms (some models already have these) and fit elastic (the round section ‘hat’
elastic is best for this). However, the presence of the elastic makes the spectacles
more difficult to put on and so we do not recommend this for the full class set. A
few pairs can be kept separate for the pupils who need them and who can be
trained how to put them on.
Goggles are a great problem for small-faced pupils. As the elastic is tightened to
make the goggles narrow where they touch the head, the housing at the forehead
and cheeks is often so distorted that it either leaves unexpected gaps or digs in,
making the goggles very uncomfortable to wear. In our guide R135, we comment
on the suitability of the different models for small-headed pupils.
Whenever there is a problem of fitting eye protection because of head shape, the
best eye protection is a six-inch face shield with elastic back adjustment, particularly if prescription spectacles are worn.
Misting
(particularly of
goggles)
Condensation sometimes forms on the outside of lenses if the wearer is near a
container of hot water but this usually clears quickly because of local air movements. However, condensation that forms on the inside of lenses is much more
difficult to clear because of poor air circulation and the perpetual presence of
moisture from the tear ducts (and from the forehead if the wearer is hot and
bothered!). Spectacle wearers suffer particularly, because there are two additional
surfaces which can mist up. One means of reducing misting when eye protection
is first put on is to keep it in a warm place, as condensation only occurs on
relatively cool surfaces. Another is to wipe the lenses with an anti-mist product.
Most suppliers sell these but usually as an aerosol or hand spray which could be a
source of disruption! These products are relatively expensive and the best
alternative is to wipe the lenses with a smear of washing-up detergent. Take care
to use a very soft cloth (see Clean with care!, below).
Most suppliers offer alternative lenses which are ‘anti-mist’. Those that have just
a surface treatment are very easily damaged but those where the anti-mist compound is incorporated in the acetate mix are useful, although their cost usually
prevents them being considered for class use. Staff, technicians and senior pupils
who have to wear eye protection for long periods may find them beneficial although these lenses do mist up after a time if the atmosphere is particularly
humid. The eye protection needs to be left in a dry atmosphere to restore the antimist properties. If purchase is considered, it is worth asking for a sample to try it
out.
Scratched lenses Spectacle wearers quickly learn that glass lenses can be scratched if the spec-
tacles are placed lens downwards on a surface. The plastic lenses used in eye protection are even more vulnerable, with polycarbonate more easily damaged than
acetate. Although deep scratches reduce the mechanical strength of the lenses,
this is not a great disadvantage in science laboratories; it is the very shallow
surface scratches that are the major problem. They are formed when spectacles
are placed lens-down on surfaces and result in foggy patches on the lenses which
make it difficult for the wearer to see what he or she is doing. These foggy patches
can be improved by polishing with a good metal polish such as Brasso. Schools
who find this worth doing might then graduate to proper acrylic polishes.
Clean with care!
It is very important to note that quite common materials can mark plastic lenses,
for example, linen tea towels and some paper tissues. Very soft tissues sold as
medical wipes appear to be satisfactory, as are the soft ‘linty’ household dusters
and old cotton handkerchiefs. Only the balls of the fingers and thumb (covered
with a cloth) should be used for rubbing lenses because any uneven pressure from
a fingernail, for example, can make further marks.
Broken lenses
Some schools have problems with goggle lenses snapping in the centre. The main
reason for this is that the pupils flex the lens too much when putting the goggles
on or off. They often take off the goggles by holding them in one hand at the nose
and pulling them away from the face and upwards until the elastic slips off from
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the back of the head. The correct way to remove goggles is to slip the elastic up
and forward with one hand while supporting the goggles with the other. The
correct way to put them on is to hold the elastic out of the way with one hand,
place the goggles in position against the face with the other hand and, only then,
slip the elastic over the head. If the goggles need to be moved slightly on the face,
then both hands should be used to pull the goggles away slightly from the face
and then replace them in position.
Acetate lenses
are more flexible
If buying new lenses, note that acetate is more flexible and less likely to snap
than polycarbonate. Both are less brittle when warm; see Storage below.
Removable ‘bits’
Because of the need, in industry, to be able to change lenses quickly or to adjust
spectacle arm length for a comfortable fit, many designs of eye protection can lead
to an inattentive class presenting the technician with a collection of bits to be
reassembled. It is worth trying to fix some of these with a dab of glue when they
are replaced. Some plastics are very difficult to glue but we suggest you try Loctite
Multibond, RS Multi-bond or similar two-part adhesives.
3.2.4
Maintenance
Most types of eye protection give rise to some problems of maintenance. No type of eye
protection is ideal for schools. Teachers who have worked with one type and solved one
or two of the associated problems are well advised to stick with the type they have
rather than cope with the new range of problems that a change would bring. There is
no doubt that careful storage and early, thorough training on the importance of safety
measures and the care of eye protection will lengthen the life of whatever type is in
use.
Cleaning and disinfection
Pupils and staff will be more willing to wear eye protection if it is clean and in good
condition. In general, routine cleaning should be done once or twice a term. Obviously
individual pieces should be cleaned when necessary. Eye protection should be washed
in a fairly strong detergent solution, rinsed and left to drain. Only polish lenses when
the eye protection is dry. Care should be taken to use very soft cloths.
The London School of Hygiene and Tropical Medicine has told us that lice cannot be
transmitted by headware. However, it is possible, although unlikely, that some eye
infections could be transmitted by eye protection. Eye protection can be disinfected
using Harris BAS solution, Gerrard ASAB (from Griffin), TEGO MHG, or similar
disinfectants used in school biology.
Storage
Pupils are more likely to take care of eye protection if they see it stored carefully. Any
thrown higgledy piggledy into a drawer or tray will become dirty and very scratched.
It is important that eye protection is kept in a warm place. Goggle housings are more
flexible when warm and will then mould to the contours of the face better than when
cold and fairly rigid. The lenses, too, are more flexible when warm and are less likely
to snap when the eye protection is flexed in the action of putting it on.
The following storage systems have been recommended.
For spectacles
One solution is to provide a series of pockets attached to a piece of cloth which is
hung up on a hook. The main considerations in design are the number of spectacles to be stored and the hanging space available. A system attached to the bottom
of a wire coat hanger will take only four spectacles across. Four rows of spectacles
(16 in all) is about the maximum for convenience and before the weight distorts
the hanger. If more width is available then it is better to hang the material from a
dowel rod.
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The pockets need to have more material in their width than the back cloth. For
each pocket 140 mm of material fixed to 100 mm of the back cloth is satisfactory;
the spare material is made into a tuck at the bottom sewn edge. Construction is
quicker if the pockets are applied in a strip. The top of the pockets can be left
loose or threaded with elastic. It is advisable to strengthen the material where it
covers the dowel rod or the wire of the hanger by having extra layers of material
or Vilene.
Scientific & Chemical Supplies sells an inexpensive goggles storage bag with 15
pockets (made of fabric); this can be used for both spectacles and goggles. Alternatively, similar systems can sometimes be bought in markets (for shoe storage) or
camping shops (for general storage). These are often made of plastic.
If hanging space is not available, a pocket system can be constructed which can be
rolled up. In this case, we would recommend that the cloth is not too wide or it is
unwieldy to roll; four or five pockets wide is manageable. For this system, elastic
in the top of the pockets is essential to stop the spectacles falling out. Also the
space between the rows of pockets needs to be adjusted to make a neat roll. For
example, if rolling from the bottom, there should be 25 mm of cloth between the
bottom two rows, 50 between the second and third rows etc. Two tapes could
secure the roll (as in dissecting instrument kits).
One school, which uses spectacles that are sold in cardboard sleeves, has suggested fixing these sleeves together with Sellotape and placing the whole in a box of a
suitable size. The sections and the spectacles can be numbered and the pupils
trained always to use the same numbered pair. This can be helpful if anyone has
an eye infection.
A similar idea is to use square section plastic drainpipe cut into 175 mm lengths.
These are packed onto a cupboard shelf to form a series of pigeonholes.
Another school has reported using a laboratory drawer divided with wooden partitions to accommodate 25 pairs of spectacles. It is reported that it is easy to lift
out when needed and provides an easy visual check on numbers. One could elaborate this and line the sections with material to reduce scratching, but putting the
spectacles into partitions is probably sufficient to prevent damage in storage.
For goggles
Many technicians and teachers have commented that there is far less problem
with goggle lenses being scratched than with spectacles because the housing
holds them away from any surface on which they are placed. Schools usually
keep them in a cardboard or wooden box. Those schools that have provided
partitioned boxes for storage have found that the easy visual check of numbers is
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a bonus. One school has made tightly interlocking dividers for its storage box,
making the whole system very sturdy.
Some schools that have sufficient wall space, hang their goggles by the elastic
from hooks or pegs. Staff have commented that the elastic does suffer from this
treatment and that it is not suitable in a very dusty room.
For face shields Some schools have face shields for all pupils to use and this presents a great
storage problem. So far, the following solutions have been suggested.
Stacking
Consider stacking them vertically one inside another in end-of-bench cupboards.
Hanging by back Consider hanging them by the back strap on a broom handle so that they hang
inside each other and storing this on hooks under a cupboard or shelf (rather like
strap
the extension-rest storage on a snooker table). The broom handle needs some
stops on the ends to prevent the face shields sliding off too readily.
Hanging by top
strap
3.2.5
The above technique is not very suitable for those with an elastic back. They can
be hung by the top strap on a right-angled hook or piece of dowel rod. The advantage is that the visor hangs vertically and becomes less dusty. The school where
this system was used had fixed a batten under a run of wall cupboards and had
screwed a row of hooks into it.
Repair
Polishing scratched lenses
The correct
procedure for
polishing lenses
Wash the eye protection to remove dust and grit which would otherwise increase
the number of scratches. Pat dry.
Polish with a soft cloth and metal polish or special Perspex polishes; use first the
abrasive grade, then the fine and then the anti-static. Use a small circular
movement and even pressure. Remember that it is the energy put into the job
rather than the quantity of polish that will bring results.
If a metal polish is used, give the eye protection a final wash in a strong detergent solution to remove the oil incorporated in the polish.
Personal safety
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© CLEAPSS 2001
Replacement
lenses
Many teachers and technicians are not aware that it is possible to buy replacement lenses for some eye protection and this is worth doing if the housing is in
reasonably good condition. However, since models change, it is advisable to buy
some replacement lenses when placing the original order.
When replacing lenses it is advisable to work in warm water which makes the
housing more flexible.
Replacement
elastic
The ribbed elastic commonly available in haberdasheries is sometimes rather
thin and will easily pull out if slotted in the usual way through the goggles’
housing. However, some shops stock bra strap elastic which can be thicker and
more suitable. In any case, it is better to purchase black rather than white
(checking the width of the slots in the goggle housing beforehand).
How to fit a
buckle
Remove the elastic from the goggles.
Loop one end round the centre bar of the buckle and sew it firmly.
Pass the free end through the slots on one side of the goggles’ housing. Then pass
the free end through one side of the buckle, over the centre bar and out through
the other side.
Pass the free end of the elastic through the slots on the other side of the goggles’
housing and sew it firmly.
3.3
Other protective clothing
3.3.1
General
Loose clothing can be a hazard in laboratories. Laboratory coats should always be
fastened and ties, scarves, etc should be prevented from hanging loose.
3.3.2
Laboratory coats
A lab coat, if done up properly, provides good protection for your clothing when handling chemicals or carrying out other routine activities. It should be washed frequently.
If you wash your coat at home, soak and rinse it alone before washing it with other
laundry in case of contamination with chemicals that could harm other clothes.
© CLEAPSS 2004
313
Personal safety
m When lab coats
It is a moot point as to whether a laboratory coat protects the person, as opposed
to the person’s clothing. A coat is useful to cover unsuitable clothing and prevent
loose items, such as ties, from causing problems. For some operations involving
large quantities of corrosive chemicals, a laboratory coat is considered inadequate
by itself and the use of an additional impervious apron is advised. A risk
assessment would be needed to determine whether a laboratory coat should be
considered as personal protective equipment and therefore provided without
charge by the employer. It is likely to be PPE for most technicians handling large
volumes of hazardous liquids.
m
There are two activities for which a lab coat is regarded as essential.
(a) The preparation of a new protactinium generator. [See section 12.10.2 (Protactinium generator).]
are needed
(b) For microbiological work at level 3, the use of laboratory coats is regarded as
an essential part of the aseptic procedures that should be followed and it is
essential to remove the coat before leaving the laboratory. The main purpose
of the coat is to protect the cultures from microbes on our own clothing. It
must therefore be very clean and freshly laundered to fulfil its function.
In these cases, the employer should provide coats for staff and some protection for
students (which could be inexpensive disposable aprons). However, all these costs
may come from the ordinary department budget rather than a separate health &
safety budget and, in many cases, students are asked to provide old shirts for work
in microbiology.
m Type of material
Pure cotton coats ignite less easily than polyester/cotton mixtures - the more
polyester the more flammable it is. Also, the thinner the material, the easier it is
to ignite. It is virtually impossible to ignite the coats with a luminous yellow
Bunsen burner flame so prevention may be the best strategy. Flame-retardant
materials are available (eg, Proban)1 and these are clearly a good idea. Nylon held
in a Bunsen burner flame tends to melt and drips of molten nylon may cause
significant burns. There has been a small number of cases of laboratory coats
(pupils’ or teachers’) catching fire. Pure cotton coats, although less liable to ignite,
tend to be hot to wear and are not readily available from most suppliers2.
Polyester/cotton mixtures are much the commonest and, though not perfect, are
satisfactory for school use if care is exercised when using Bunsen burners.
m Oxidising agents
There is a danger that oxidisers, if allowed to dry onto combustible material could
give rise to a serious fire risk. There are no authenticated cases of this occurring in
schools but spills of any chemical with the oxidising symbol should always be
cleared up with special care to avoid contamination of wood or cloth. If a
laboratory coat becomes contaminated, it should be washed immediately.
3.3.3
Gloves
m Gloves are also personal protective equipment3. Different types of glove all have their
uses and none is suitable for every job. Ordinary kitchen gloves are used in many situations but they should be taken off quickly if a concentrated acid or other corrosive
chemical splashes on them, as the protection they give from such chemicals can be
short-lived. Nitrile gloves are probably the best for general-purpose use in school
science and these are now available in relatively comfortable, well-fitting and inexpensive designs. Beware that allergy to latex is quite common, especially with powdered
gloves. Heat-resistant gloves are made of leather or thick cotton. These offer good
insulation but char or burn when touched on red-hot objects. An alternative is to use
silicone rubber grippers, usually described as ‘hand/finger protectors’ in suppliers’
catalogues. See also section 20.12 (Gloves) for discussion of glove types and uses.
1
Proban is available from Rhodia.
2
Cotton drill coats are available from Alexandra and Timstar Laboratory Suppliers.
3
See CLEAPSS leaflet PS50, Gloves as Personal Protective Equipment (PPE).
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© CLEAPSS 2005
m Technicians will often need to wear gloves because they are handling large quantities
of hazardous chemicals, the identity of which (when clearing up) may be unknown.
When wearing some types of gloves, technicians may feel that a loss of manual dexterity increases the risk of accidents. There will be some situations when gloves are
essential, eg, opening a bromine ampoule but, in general, risks should be assessed,
bearing in mind the recommendations on the relevant Hazcard. If gloves are not worn,
facilities to wipe or wash off spilt chemicals must be immediately available.
m Pupils
rarely have to wear gloves. Manual dexterity is lost, gloves may encourage
carelessness and risks from the tiny quantities handled by pupils are small. However,
gloves are required, eg, when handling chemicals such as phenol or when ninhydrin is
sprayed. See individual Hazcards for guidance on when pupils need to wear gloves.
3.3.4
Footwear
m Special
footwear is rarely needed, but strong shoes may be advisable. If handling
heavy equipment, steel toe caps may be a good idea. Sandals or open shoes are inappropriate for work with corrosive chemicals or heavy masses! Consider wearing Wellington boots (inside any trousers) when using large volumes of hazardous liquid.
m Where hazardous liquids may have trickled down legs into footwear, it is important to
remove the shoes or boots quickly so that feet can be washed thoroughly. In this
context, laces are more quickly undone than buckles.
3.3.5
Respiratory protection
Schools will never need to use powered respirators, breathing apparatus or ‘gas
masks’. Special training in their use is required and the equipment needs regular
checks and/or replacement. In the event of a spill of large quantities of hazardous volatile liquids in an unventilated area, it may be necessary to call the fire brigade.
m Generally, when handling hazardous gases or volatile hazardous liquids on anything
but the smallest scale, schools should use fume cupboards. However, technicians may
occasionally need to use small masks which fit over the nose and mouth, for example,
when cleaning out a particularly smelly cupboard or when handling a fine dust which
could cause sensitisation (eg, weighing out enzymes or cleaning out a locust cage).
These may be fold-flat or cup-shaped masks, some with a valve.
It is important to use the right type of mask for a particular job. Except for those
designed to protect just from nuisance dusts and odours, masks should conform to the
European Standard EN 149, updated in 2001. The degree of protection, as indicated in
Table 3.2, is based on allowing safe working when dust or vapour concentration is, or
could be, several times the Workplace Exposure Limit (WEL) (see section 7.9.1).
Table 3.2
Use of face masks
EN 149
Typical uses
Protection factor
No standard
Nuisance dusts only
-
FFP1
Dusts with large coarse or fine neutral particles; suitable for ‘craftwork’
4 × WEL
FFP2 [S/SL]
As FFP1 + welding fume, mildly toxic fine dusts; glass fibres; lead dust
& fume; asbestos
10 × WEL
FFP3 [S/SL]
Spores, bacteria, proteolytic enzymes, radioactives, carcinogens
20 × WEL
m Thus, where wood dust in workshops cannot be controlled by local exhaust ventilation,
FFP1 would be suggested, but some science activities might need FFP2 or 3.
Masks vary in their comfort but, as they will be worn infrequently, this is less of an
issue than with eye protection. Masks give poor protection when worn over beards.
© CLEAPSS 2004
3.4
315
Personal safety
Hair
Under most circumstances, hair is not very combustible. However, occasional incidents
have highlighted conditions in which the risk of hair catching fire can be greater.
m The degree of fire hazard from combustible materials is greatly affected by the surface
area exposed to the air; loose straw will burn much more fiercely than a compressed
bale. Similarly hair that is styled in an open manner can burn much more readily
than hair that is combed down flat. We are convinced that this is a more important
factor than the type (if any) of hair preparation used, although it would obviously be
imprudent even to enter a laboratory immediately after applying a lacquer from which
solvent could be still evaporating. Persons with open hair styles should be particularly
careful when working near flames.
m Long, loose hair should be tied back while working in a laboratory.
3.5
Eating and drinking
m Eating
and drinking in laboratories and preparation rooms should not normally be
allowed since accidental contamination of food used in laboratories can and does occur.
Similarly, refrigerators containing chemicals and biological materials must not be
used for storing food for human consumption. (See also section 15.13.)
However, sometimes there is no practicable alternative. If there is unlikely to be
chemical or microbiological contamination, eg, in a preparation room used for physics,
then there would be little risk. In a large preparation room with a ‘wet area’ and an
‘office area’ it may well be possible to ensure that the latter is uncontaminated.
m A risk assessment should be carried out and outcomes recorded in the science depart-
ment health and safety policy. It would be particularly important to show how food
and drink items are kept separate from everything else.
When experiments involving food are carried out, it is worth arranging for the class to
be transferred to the home economics department for the session, especially if the food
is to be tasted. This may seem a nuisance but it minimises the risks and also reinforces the special nature of laboratories in the pupils’ minds.
3.6
Hygiene
Hygiene is important in all types of laboratory and particularly so where any microbiological work is carried out or animals and plants are handled. Spills of chemicals or
biological material should be cleared up straight away and contaminated areas and
the hands etc washed thoroughly. (See sections 14.13, 15.2.14 and 15.12.3.)
Smoking in laboratories is particularly unwise; some chemical vapours can be modified on passing through a cigarette so that they become much more hazardous.
3.7
Lifting and transporting (Manual handling)
m The
handling of resources, ie, equipment, materials etc, by employees is subject to
specific regulations1. While the lifting and transporting of really heavy objects is
seldom necessary in school science, science technicians spend a substantial proportion
of their time moving equipment. Overwork or just familiarity can lead to
carelessness, and carelessness to a strained back! Manual handling injuries are the
single most-common causes of reported accidents to school staff, as, indeed, to employees in general. Special care must be taken if a technician is pregnant and should also
be considered if a technician is of slight stature etc.
1
Manual Handling Operations Regulations. The Approved Code of Practice for the Regulations is very helpful. L23 Manual
Handling (Manual Handling Operations Regulations) Guidance on Regulations, HSE, ISBN 071762823X, HSE Books, 2004.
Personal safety
316
© CLEAPSS 2007
m It
is a requirement that the manual handling of resources is minimised. Employers
have a duty to protect their employees’ backs and employees have a duty to cooperate
with their employers by using whatever control measures are necessary. Trolleys
should be used for heavy items and care taken when these are lifted on or off; see
section 8.5.2 (Types of storage). In addition to normal laboratory trolleys, a trolley
suitable for moving large cartons, ie, a sack truck, is also useful. For carrying bottles,
see section 7.4.1 (Carrying and dispensing corrosive liquids).
m Storage
should be arranged to minimise lifting; frequently-used resources should be
stored at a convenient height. Sometimes it is possible to fit ramps to aid the use of
trolleys. If a set of heavy items, eg, low-voltage power supplies or books, has to be
moved frequently between different sites or between floors without a lift, priority
should be given to the purchase of another set. Consideration should also be given to
moving pupils rather than moving heavy items, although this may sometimes be
counter-productive in terms of behaviour.
m Trays and stacking boxes are a convenient way of carrying equipment. They must not
be filled to the extent that they become too heavy. This may mean several extra
journeys with lighter loads. It must not mean that technicians have to rush to
complete other tasks. The work load needs to be adjusted accordingly.
m There can sometimes be a conflict between the requirements of the Manual Handling
Operations Regulations and the Regulatory Reform (Fire Safety) Order. The latter
may require heavy fire doors which have to be kept closed at all times, but attempting
to carry a loaded tray through these may present a significant manual-handling risk.
It is possible to fit magnetic catches which are automatically released when the fire
alarm sounds. Fitting such a system in an average secondary school would probably
cost about £20 000, but some systems1 can be fitted to individual doors, where there is
a particular problem. This would cost about £70 + VAT per door. As an alternative, it
is possible to fit an adjustable door closer2. With a closer, a door can be opened to 90 °
and is then held open, say, for 20 seconds (long enough to wheel a trolley or carry a
tray through), before closing slowly and then gradually more quickly. The speed of
closing can be adjusted when the unit is installed.
If neither magnetic catches nor door closers can be fitted, a risk assessment should be
carried out. This would show that the risk of manual-handling injury is much greater
than the risk of fire and therefore it is more important to take steps to deal with the
former. An HSE inspector, after being asked to visit one school, confirmed that it was
acceptable for doors to be held open, eg, by wedges or hooks, but steps should be taken
to remove such devices as soon as possible. The findings of such a risk assessment
should be recorded briefly in the science department’s health and safety policy.
Good practice in lifting equipment
m Keep the back straight and avoid twisting it. Bending the legs, at the
knees, should be used for raising and lowering. Any turning should
be done by moving the feet.
Other points are given overleaf3.
1
A suitable system is manufactured by Dorgard Ltd.
2
For example, the Briton 2130 door closer made by Ingersoll Rand. It can be ordered from www.doorfurnituredirect.co.uk or
http://websites.uk-plc.net/LockcentreB2Bcom/.
3
All the figures in this section are taken from L23 Manual Handling. (Manual Handling Operations Regulations) Guidance on
Regulations. ISBN 071762823X, HSE Books, 2004. Illustrations are reproduced with the permission of Her Majesty’s Stationery
Office.
© CLEAPSS 2001
m Assessment of
risks before
starting
317
This is particularly important for items which are not commonly
moved. It is important that the whole operation is considered in
advance and routes are planned: eg, it is easy to lift a heavy object
and then find no hand is free to open a door!
As much as possible, avoid lifting above the shoulders and from
below the knees.
School staff are usually unaccustomed to much handling of heavy
objects and can tire quickly; this can lead to carelessness and back
strain. Therefore, tasks, such as rearranging storage, may need to
be tackled in stages.
m The lifting
position
If the object is on a shelf, etc, slide it to the edge so that it can be
lifted close to the body.
Test the weight of the object. Can it be lightened by partial
unpacking etc?
Stand comfortably, square on to the load and close to it, with the
back straight.
The back should be kept in its natural line and the knees bent but
not too much.
Grasp the load firmly, looking out for sharp edges, staples etc.
Raise your head.
m The lifting action
The feet should be neither together nor too far apart.
Lift steadily with the legs, keeping the load as close to the body as
possible.
m Carrying
Continue to keep the load close to the body, with arms tucked in.
Continue to keep the back straight and untwisted.
m Putting down
Consider sliding the object into its final position.
Face the place where the object is to go, turning the whole body.
In lowering the object, keep the back and head straight and do not
twist to one side.
Be careful to avoid trapping fingers and toes.
m Heavy objects
Before the manual handling of heavy items, eg, carrying a tray of
power packs up stairs, risks should be assessed to see whether a
second person should be involved. In the case of power packs, it
might be safer not to carry the whole tray, but to carry the items
individually, perhaps two at a time.
Risk assessments are likely to conclude that certain items, such as
TV sets and vacuum pumps, always require two people.
It is worthwhile prominently labelling heavy items with their
mass.
If you are working with somebody else:
•
if possible, work with someone of similar size;
•
agree in advance on the whole operation;
•
put one person in charge, to call the signals.
Personal safety
Personal safety
318
© CLEAPSS 2004
Individuals vary enormously in their capacity to lift different loads. The diagram
below is therefore only guidance. Note that the figures given are not safe ‘load’ limits.
However, it does serve to emphasise the differences between men and women in this
respect and how the capacity varies when the load is held at different distances from
the body. It would be a useful starting point for a risk assessment.
10kg
3kg
5kg
7kg
Shoulder height
Shoulder height
20kg 10kg
7kg 13kg
Elbow height
10kg 16kg
Elbow height
25kg 15kg
Knuckle height
Knuckle height
Mid lower leg height
7kg 13kg
20kg 10kg
3kg
10kg
Mid lower leg height
7kg
Women
5kg
Men
m Brief training in lifting should be given to lab technicians on appointment. Very brief
retraining should be included for all staff in occasional departmental meetings.
m Pupils
will not normally have had such training, their lifting capacities will be different to those of adults and they may be tempted to show off by lifting excessive loads.
Therefore, pupils should not normally be used for carrying items around the school
and certainly not those which are heavy or awkward in shape. A class set of books can
be quite heavy!
3.8
Safety screens
3.8.1
When to use
m Safety
screens should be used whenever there is a risk of explosion, implosion or
projection of hot materials. They should also be used to prevent inadvertent contact
with exposed conductors at voltages greater than 40 V with respect to earth; see section 6 (Mains electricity). At least two safety screens are required to protect both the
demonstrator and the audience.
A fume cupboard should not be used as a substitute for a safety screen on a laboratory
demonstration bench, unless toxic fumes are also evolved during the activity requiring
the protection of a screen. Carrying out procedures such as the thermit reaction or the
‘howling jelly-baby’ demonstration in a fume cupboard may damage the glazing. If the
fume cupboard is made of plastic material, the damage can be permanent (and
expensive to repair).
It is important to realise that safety screens provide only back-up protection should an
accident occur. The first consideration in setting up any demonstration that carries a
risk of explosion, shock etc should be to perform the demonstration in a safe way,
minimising the chance of an accident by taking appropriate precautions.
Whenever safety screens are used because of the risk of an explosion, eye protection
should also be worn by everyone in the room.
It should be noted that failure to use a safety screen and eye protection during a demonstration contributed to the prosecution of a teacher. While passing hydrogen over
copper oxide, the teacher lit the hydrogen before all the air had been removed from the
apparatus. The explosion sprayed acid and broken glass over the pupils.
© CLEAPSS 2004
319
Personal safety
If there is only a single safety screen available, pupils could be sent to the back of the
laboratory while the demonstrator is protected. This is appropriate for demonstrations
of the thermite reaction or fat-pan fires but not for the reaction of sodium or potassium
on water, which requires relatively close observation.
Demonstrations for which a safety screen should be used
The list in Table 3.3 is not exhaustive but is intended to indicate the type of demonstration for which we think screens are required. A fuller list can be obtained by
typing “safety screen” in the Acrobat search-engine facility on the CLEAPSS Science
Publications CD-ROM.
Table 3.3
Demonstrations requiring the use of safety screens
Activity
Reference
AC power lines
Handbook 12.9
Air rifle experiment
Handbook 12.4
Burning calcium
Hazcard 16
Burning potassium
Hazcard 76
Burning sodium
Hazcard 88
Calorimetry - fuel and food combustion
Safety in Science Education1 p61
Carbon monoxide/metal oxide reactions
Hazcard 21
Catalytic oxidation of ammonia gas
Hazcard 5
Combustion of gases
Handbook 13.4
Conductivity of electrical current through molten glass
Handbook 12.9
Decomposition of ammonium nitrate
Hazcard 8
Diffusion of gases (eg, bromine) demonstrations
Hazcard 15, Guide L195
Distillation under reduced pressure
Safety in Science Education p61
Electrolysis of molten hydroxides
Hazcard 91
Electron beams
Handbook 12.6
Ethyne preparation
Hazcard 19
Fountain experiments: ammonia, hydrogen chloride and sulfur dioxide
Hazcards 5, 49, 97 Handbook 13.2
Generating hydrogen in demonstrations
Hazcard 48
Heating lithium
Hazcard 58
Hydrogen burning if gas generated by chemical means
Hazcard 48
Hydrogen/metal oxides reactions
Hazcard 48; Handbook 13.2
Magnesium/copper oxide reaction
Hazcards 26, 59; Handbook 13.2
Magnesium/silicon dioxide reaction
Hazcard 59
Magnesium/steam reaction
Hazcard 59
Magnesium/sulphur dioxide reaction
Hazcard 97
Mains electric arc
Handbook 12.9
Manganate/propan-1,2,3-triol reaction
Hazcard 37
Methane explosion (exploding tin)
Hazcard 45
Potassium/water reaction
Hazcard 76; Handbook 13.2
Preparation of dinitrogen monoxide
Hazcards 8, 68
Preparation of potassium manganate(VII)
Hazcard 60
Sodium fusion test
Hazcard 88
Sodium/water reaction
Hazcard 88; Handbook 13.2
Thermit reaction
Hazcard 11; Handbook 13.2
Vacuum pump activities
Handbook 12.20
Zinc/sulfur reaction
Hazcard 107; Handbook 13.2
1
Safety in Science Education, DfEE, 1996, HMSO, ISBN 011270915X.
Personal safety
3.8.2
320
© CLEAPSS 2004
What to use
Safety screens are not constructed to any recognised British or European standards.
Materials
The materials used to make the safety screens available from educational suppliers
are acrylic1 and polycarbonate. For school science, the less expensive acrylic safety
screens are quite suitable. Another material, PET (polyethyleneterephthalate), is
available from local sources if a screen is constructed by school staff; see section 3.8.4.
Size and thickness
In the past, CLEAPSS has recommended that the thickness of safety screens should
be 6 mm, but most manufacturers now supply 3 mm screens. Thinner screens are less
expensive and, as there have been no reports of such screens shattering or catching
fire during practical activities, there is no reason why they should not be used. The
only problem that may occur is that they are less stable and a 3 or 4 mm-thick screen
will always need base support.
Commercial safety screens can be expensive. A sheet as large as 1000 mm × 750 mm
may be required but it can be useful to have smaller screens as well; these can be
easier to work around for some demonstrations. A plastic sheet can also be placed over
a trough when demonstrating the reaction of potassium or sodium with water.
Buying safety screens
This can be an expensive outlay. There is considerable variation in the type and price
of safety screens sold by the various educational scientific equipment suppliers, with
similar items retailing at very different prices from different companies. CLEAPSS
Guide R135, Eye and Face Protection, compares product availability and, even if the
current edition was compiled some time ago, gives an indication of what to look for.
3.8.3
How to use
Safety screens are usually required in pairs to protect the demonstrator as well as the
pupils.
They should normally be placed in front of and behind the apparatus and positioned so
that they shield the complete experimental set-up. It is important, but often forgotten,
to ensure that no pupils are situated to the side of the demonstration where they have
direct sight of the apparatus not through the screen.
The teacher should work from behind the rear screen, manipulating apparatus around
the sides. Careful consideration of the positioning of the apparatus, particularly parts
that require manipulation is required here. Positioning of equipment may also be
dictated by requirements for gas, electricity or water. As already stated in section
3.8.2, smaller screens are sometimes of use to aid easy manipulation.
Screens must, of course, be held firmly upright and slotted bases are often used for
this, although a G-clamp is advisable to secure the base firmly to the edge of the
bench. D-i-y supports may be constructed similar to those shown in the illustration
overleaf. It is possible in some circumstances to make use of a large wooden base with
support for the screen along all of its length but this type can be awkward to place on
some benches due to the positioning of gas taps etc.
1
The chemical name is polymethyl methacrylate. Perspex is an ICI-registered trademark for its sheet product.
© CLEAPSS 2004
321
Personal safety
The diagrams below illustrate how the shape of a safety screen affects the positioning
of pupils.
Isolating an activity if services are situated on a side bench
Wall
Wall
Services
Services
Activity
Activity
Screen
Screen
Teacher
Teacher
Pupils
Pupils
In the diagram above on the left, the activity (eg, transmission-lines demonstration) is
isolated with a straight safety screen. The teacher is positioned so that he/she can only
control the services such as gas or electricity and not gain access to the activity itself.
The pupils have to be arranged so that they are protected from explosion or any
temptation to touch the equipment behind the screen. With this screen, the pupils
would be crowded together into a small area as shown. The use of a 3-panelled screen
(above on the right) would allow more protection to the teacher and pupils could be
seated over a wider area.
Isolating an activity if services are situated on a demonstration bench
Teacher
Teacher
Screen A
Services
Activity
Screen A
Services
Activity
Screen B
Pupils
Screen B
Pupils
Personal safety
322
© CLEAPSS 2004
In this situation, at least two screens are required to protect both the pupils and
teacher. Again, a 3-panelled screen allows the pupils to be positioned within a larger
area. If bench space permits, three straight-sided screens can be used to enclose
apparatus.
There are times when a teacher needs to prepare or manipulate materials during a
demonstration in front of a class protected by a screen; eg, the thermit reaction, or
adding sodium to water. Although screen A in the diagrams overleaf could be removed
and the demonstrator wears a face shield for added protection, it would be better to
reach around the end or through a small gap if possible.
Safety screens should be placed as close to the equipment as possible so that, if something is projected vertically, eg, a piece of burning sodium, it is unlikely to fly over the
screen and fall on the pupils. However, this may not be possible if a Bunsen burner is
used or the reaction produces lots of sparks, both of which may damage the screen. In
such cases, pupils should be positioned further from the demonstration.
Demonstration
bench on a higher
level than students
Taller safety screens
required to provide
same level of
protection
Demonstration
bench on the
same level as
students
Position of students
When demonstrating using a bench at the same level as the students, it would be
advisable to use taller screens. Screens of the required height may not be commercially available and need to be constructed (see section 3.8.4).
3.8.4
Making your own safety screens
The advantages of making one or more safety screens in-house are that:
•
•
•
they are relatively inexpensive compared with commercial screens,
they can be made larger than commercial screens,
the dimensions of the screens can be adjusted to fit the size of demonstration
bench and the normal arrangement of pupils around the bench.
Obtaining plastic sheet is relatively straight forward, especially if the school is in or
near a town. Look under ‘Plastics - stockholders’ in Yellow Pages. Prices vary, so it is
sensible to obtain a number of quotes.
However, when visiting a supplier’s warehouse, it is possible to obtain off-cuts, not
only of acrylic or polycarbonate but also of PET (polyethyleneterephthalate). This
material is more dense, easier to drill and chemically more inert than polycarbonate or
acrylic. We were able to obtain three 690 × 470 × 6 mm sheets free. Suppliers have to
pay for their waste to be removed, so some are only too willing to give away the plastic
sheets to schools if transportation can be arranged.
There are also suppliers trading on the internet. One quote of £107 was obtained for a
sheet of polycarbonate with the dimensions 2050 × 1525 × 3 mm. This could be cut as
shown overleaf to make single screens of various widths or two free-standing folding
screens.
© CLEAPSS 2004
323
Personal safety
2050 mm
1525 mm
It is possible to hinge together three sheets of polycarbonate or PET with nylon cable
ties, as shown below. Acrylic is difficult to work with because drilling can cause cracks
to occur in the sheeting.
After the sheet is cut to size, sharp edges should be smoothed down with a file. The
holes should be drilled slowly (to avoid the sheet cracking) about 15 mm from the edge.
After attaching the ties, they should be cut right down so that no sharp edges
protrude. If the screen is made using PET, polycarbonate or 5 mm acrylic sheets, it
can be free-standing. With lighter 3 mm sheets, grooved pieces of soft wood must be
constructed to aid stability. The sheets fold away so that the safety screen is easy to
store and carry.
Care of safety screens
Screens are easily scratched, especially as they are loaded onto trolleys for transportation between the prep room and laboratories. It is not difficult to make a cover from
two pieces of remnant material cut to size and stitched around 3 sides of the screen.