LASER SAFETY
Laser Classification
It is the responsibility of the laser manufacturer to provide the correct classification of a
laser product. This classification is made on the basis of a combination of output power(s)
and wavelength(s) of the accessible laser radiation over the full range of capability during
operation at any time after manufacture which results in its allocation to the highest
appropriate class.
Maximum Permissible Exposure Levels (MPE)
Maximum Permissible Exposure limits are those levels of laser radiation to which, in
normal circumstances, persons may be exposed without suffering adverse effects. A
guide to MPE levels are given in BS EN 60825-1. They are based upon biological data
collected to date.
Laser Classes
Lasers are grouped according to ability to do harm, the higher the number the greater the
harm. The current laser classes are 1, 1M, 2, 2M, 3R, 3B and 4
Class 1
ƒ
Safe under reasonably foreseeable conditions of operation.
ƒ
The most limiting MPE values cannot be exceeded and no specific safety controls are
required.
ƒ
For CW (Continuous Wave) visible lasers, the maximum limit is 70 microwatts.
ƒ
Class1 operation cannot be claimed for a product containing an embedded laser of a
higher class unless full-interlocked high-integrity enclosures using fail-safe interlocks
are incorporated.
ƒ
Class 1M is a large diameter or widely divergent beam (302.5 – 4000 nm). As Class 1,
but not safe when viewed with optical aids such as binoculars or eye loupes.
Class 2
ƒ
Visible lasers only, for which the MPE cannot be exceeded in less than 0.25 seconds.
The eye is protected by the aversion responses, including blinking reflex and head
movement.
ƒ
For CW (Continuous Wave) laser the limit is 1 mW.
ƒ
Class 2M is a large diameter or widely divergent beam. As class 2, but not safe when
viewed with optical aids such as binoculars or eye loupes.
safetyunit@gre.ac.uk
April 2009
Page 1 of 5
Class 3R (Previously Class 3A)
NB: where reference is made to Class 3R, the same applies to the previous classification of 3A.
ƒ
Wavelength 302.5 – 106 nm
ƒ
Lower risk than 3B, but direct viewing of beam potentially hazardous.
ƒ
Visible lasers up to five times the Class 2 limits and invisible lasers up to five times the
Class 1 limits, for which specific H (Jm-2) or E(Wm-2) values are not exceeded.
Class 3B
ƒ
Visible and invisible lasers not exceeding specified limits, which are 0.5W for CW
(Continuous Wave) lasers and 105 Jm-2 for pulsed lasers (less for ultraviolet
wavelengths).
ƒ
Direct beam viewing not safe to the eye, specularly reflected beams e.g. reflected from
shiny surfaces may also be harmful to the eye; diffusely reflected beam usually safe to
the eye, assumed to be safe to the skin.
Class 4
ƒ
Those that exceed the limits of Class 3B.
ƒ
Viewing a direct beam or a reflected beam is always harmful to the eye and skin,
diffusely reflected beams should be assumed harmful to the eye or skin unless proven
otherwise, both scattered and reflected beams can present a fire hazard.
Laser System
A laser system is a system containing one or more lasers associated with a single
application or process and under the control of a single operator, i.e. lasers that are
exchanged on the same system or are running simultaneously on the same experiment
(e.g. pump laser and main laser). There is more than one laser system if the lasers are
not operating together or are used by different operators although mounted in the same
area.
Laser Product
A laser product is a piece of equipment containing a laser system. The product may be
given a low classification even though it contains a higher classification system, provided
that there are engineering controls to prevent access to the totally enclosed embedded
system. Common examples are CD players, laser printers and some scientific analytical
equipment.
Risk Assessments and Written Procedures
The Management of Health and Safety at Work Regulations require a risk assessment of
all work activities. The risk assessment should identify the key hazards at all stages of the
work. The risk – the likelihood and severity - of harm occurring to those carrying out the
work, and any others who may be affected by it, must be assessed and suitable
precautions identified and implemented to minimise the risk of those hazards causing
harm. The risk assessment must be recorded in an approved format (see Code of
Practice on risk assessment and School/Office procedures).
Page 2 of 5
Hazards associated with laser equipment
Risk assessments must be carried out where use of work equipment involves possible
exposure to significant hazards. In carrying out a risk assessment for work with lasers,
consideration must be given to the optical and skin hazards of the laser radiation itself due
to open beam paths, misalignment problems and the mounting of optics. This applies to
the use of all classes of laser but particular attention is required in the case of Class 3 and
4 lasers due to the level of hazard.
However, the risk assessment must also consider other hazards associated with use of the
equipment, the main ones being:1. Electrical – high voltages
2. Chemical/Fume – sample preparations, use of dyes and solvents, fumes produced by
cutting and engraving (apply COSHH Regulations)
3. Mechanical – manual handling materials and gas cylinders, falls when accessing high
parts of the equipment, slips and trips on cables, cryogenic liquids, noise, vibration
4. Fire – high power, direct and reflected beams, ignition of cut materials
5. X-rays/electromagnetic interference
All stages of the installation, use, routine maintenance, periodic servicing, and disposal of
the equipment must also be considered in the risk assessment, whether this is carried out
by staff, students or contractors.
The complexity of the risk assessment should be relevant to the class of laser, i.e. for
Class 1 and 2 lasers, the risk assessment will be far simpler than for a Class 3B or 4 laser.
Summary of Manufacturer’s and User Requirements for Lasers
(From the AURPO Guidance Note No.7 2007)
Remote interlock -
connection provided by the manufacturer for door or enclosure interlock for Class 3B
and Class 4 lasers
Safety interlocks -
required for access panels on Class3R, 3B and 4 laser systems
Key control
a key or similar device is required to control unauthorised operation of Class 3B and
Class 4 lasers
Emission indicator -
an audible or visible indicator should be provided by the manufacturer for each Class
3R laser ( except wavelengths 400-700nm) and each Class 3B and Class 4 laser
system
Beam stop or
attenuator/shutter -
should be provided by the manufacturer for each Class 3B or Class 4 laser system
Beam termination -
the user should ensure that all beam paths are terminated at the end of their useful
path. (Does not apply to Class 1 devices)
Beam level -
avoid eye level
Beam enclosure -
to guard against specular reflections from Class 3R, Class 3B and Class 4 lasers can mean anything from screening the experimental area or piping the beam up to a
total enclosure.
Eye protection -
required for open beam work with invisible beam Class 3R and all Class 3B and
Class 4 devices.
Page 3 of 5
Protective clothing
mainly required for Class 4 lasers but be careful with Class 3B UV lasers as well,
may need fire resistant material for some lasers
Eye examinations -
only required after an accident but may be important to people with poor eyesight
working with Class 3B or Class 4 lasers
Training -
required for people working with any Class 3 or Class 4 laser and any modified Class
1M or Class 2M devices.
Laser labels -
required for all lasers except low power Class 1 ( though need not be directly affixed
if the size of the laser product does not permit this)
Door/Area signs -
required for Class 3B and Class 4 lasers indoors and also for Class 1M, 2M and 3R if
used outdoors
Summary of precautions for each laser classification
Precautions
1M
2
2M
3R
Remote Interlock
n/a
n/a
n/a
n/a
Safety interlocks
n/a
n/a
n/a
Key Control
n/a
n/a
n/a
Emission indicator
n/a
n/a
n/a
Beam Stop/Shutter
n/a
n/a
n/a
Beam Terminator
3B
4
1(E)
n/a
n/a
n/a
n/a
n/a
n/a
Beam Level
n/a
Beam Enclosure
n/a
n/a
n/a
Eye protection
n/a
n/a
n/a
Protective Clothing
n/a
n/a
n/a
n/a
n/a
Eye Examinations
n/a
n/a
n/a
n/a
n/a
n/a
n/a
n/a
Training
n/a
n/a
Laser Labels
Door/area signs
n/a
n/a
NB Class 1(E) indicates a Class 1 totally enclosed system
Designated Laser Area
A Designated Laser Area (DLA) is an area or room where one or more Class 3B and/or
Class 4 lasers are in use. Signage is mandatory at the entrance to the area/room.
Eye Protection
Protective eyewear is a common and important aspect of personal laser protection
wherever there is some risk of laser exposure above the specified MPEs. However, it
does not replace a full risk assessment and consideration of all alternative means of
affording protection – such as total enclosure of the beam, interlocks, beam dumps etc.
Page 4 of 5
Laser safety eyewear, safety glasses, are the last line of defence and not a convenient
alternative to avoiding any engineering controls that it may be possible to implement.
Laser safety eyewear incorporates optical filters to reduce the laser radiation to below the
level of the MPE, whilst at the same time maintaining a reasonable level of visible light
transmission.
The filter damage threshold must be sufficiently high to withstand the maximum possible
exposure long enough for appropriate avoiding action to be taken. The absorbance of the
filters must be appropriate to the wavelength of the laser(s) used. Clear information must
be available to identify the eyewear that is suitable for each laser and whether it is for
alignment work or full protection.
Standards for laser eye protection are BS EN 207 (for normal use) and BS EN 208 (for
maintenance and adjustment work). Eye protection must conform to these standards and
be clearly marked to indicate the protection that is provided.
Users are responsible for exercising care in the use and storage of eye protection. These
items are expensive and easily scratched, degrading performance and comfort. Any
defects must be notified to the user’s supervisor and work requiring the defective item
should cease until a safe replacement is made.
Relevant Standards and Guidance
University sector guidance is given in the Association of University Radiation
Protection Officers (AURPO) Guidance Note No.7 Guidance on the safe use of lasers
in education and research. This can be downloaded from www.aurpo.org/docs It
replaced the CVCP Notes of Guidance Part 2.1 Lasers, 1992.
More detailed guidance on best practice in the use of lasers is given in:
ƒ
British Standard BS EN 60825-1:2007 Safety of laser products - Part 1:
Equipment classification and requirements.
ƒ
PD IEC TR 60825 – 14:2004 Safety of laser products – Part 14: A user’s guide
(originally included in Part 1 of the British Standard)
ƒ
BS EN ISO 11553-1:2005 Safety of machinery – Laser processing machines –
Part 1: General safety requirements sets out requirements for equipment such as
cutting and engraving machines used in design and technology workshops.
ƒ
BS EN 60825-2:2004 Safety of laser products – Part 2: Safety of optical fibre
communication systems (OFCS) defines requirements covering the safety of fibre
optic networks.
ƒ
IEC/TR 60825 3:2008 Safety of laser products – Part 3: Guidance for laser
displays and shows sets out the precautions which should be observed by organisers
of events.
ƒ
INDG224 Controlling the radiation safety of laser display installations is available
together with other information on the Health and Safety Executive website
www.hse.gov.uk
The Health Protection Agency website includes information about laser hazards and
precautions, including laser pointers. See www.hpa.org.uk
Page 5 of 5