Risk Assessment Guidance
The assessor can assign values for the hazard severity (a) and likelihood of occurrence (b)
(taking into account the frequency and duration of exposure) on a scale of 1 to 5,
then multiply them together to give the rating band:
Hazard Severity (a)
Fatal
Serious
Moderate
Minor
(eg discomfort, slight bruising, self-help recovery)
(eg small cut, abrasion, basic first aid need)
(eg strain, sprain, incapacitation > 3 days)
(eg fracture, hospitalisation >24 hrs, incapacitation >4 weeks)
(single or multiple)
Trivial
1 – Trivial
2 – Minor
3 – Moderate
4 – Serious
5 – Fatal
Likelihood of Occurrence (b)
Remote
1
2
3
4
5
2
4
6
8
10
1 – Remote
2 – Unlikely
3 – Possible
4 – Likely
5 – Very likely
(almost never)
(occurs rarely)
(could occur, but uncommon)
(recurrent but not frequent)
(occurs frequently)
The risk rating (high, medium or low) indicates the level of
response required to be taken when designing the action plan.
Rating Bands (a x b)
LOW RISK
(1 – 8)
MEDIUM RISK
(9 - 12)
HIGH RISK
(15 - 25)
Unlikely
Possible
3
6
9
12
15
Likely
Very
likely
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4
8
12
16
20
5
10
15
20
25
Continue, but
review periodically
to ensure controls
remain effective
Continue, but
implement
additional
reasonably
practicable
controls where
possible and
monitor regularly
STOP THE
ACTIVITY
Identify new
controls. Activity
must not proceed
until risks are
reduced to low or
medium level
University Health, Safety & Environment Service
Risk Assessment Record
Persons
affected
and how
Existing controls & measures

1
Use of gas cylinders
 Manual handling injury
 Cylinder falling over - impact
 Cylinder exploding – flying debris,
impact
 Damage to regulator/ valve uncontrolled release of high
pressure gas. Cylinder potential
projectile.
 Compressed gas - User potentially
exposed to jet of high pressure gas.


Worker and
others in the
area




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Refer to the generic RA on ‘Storage and use of gas
cylinders’ for the transport and handling of the
cylinders
Users must be trained and competent to handle
cylinders and fittings
The cylinder must be transported wearing gloves, and
using a cylinder trolley. Short distances may be
covered using the “milk-churning” technique.
Cylinders must be secured (e.g., strapped to bench or
chained to wall) and never left free-standing.
Never transport a cylinder with the regulator attached.
Do not attempt to catch a falling cylinder - get out of
the way.
Double check that the correct gas is being used, in
addition to the correct regulator and equipment that is
compatible with the gas.
Risk rating
(a x b)
Hazard(s) identified
Standard for use across department.
Likelihood
(b)
#
Assessor(s):
Date:
Dr Robyn Bott (Safety Coordinator)
July 2015
General use of hydrogen gas cylinders in the lab environment. This risk assessment does not
cover the experimental procedure - this must be COSHH assessed before work starts.
Context of assessment (delete as appropriate or describe):
Severity
(a)
Risk Assessment of:
Use of Hydrogen Gas Cylinders
Overview of activity/ location/ equipment/
conditions being assessed:
Generic or specific assessment?
Generic
3
2
6
Additional
controls
required
University Health, Safety & Environment Service

Hydrogen Gas
 Fire/ explosion
 Asphyxiation

CAS: 1333-74-0
H220 - Extremely flammable gas
H280 - Compressed gas, may explode if heated
Hydrogen is odourless and colourless, so leaks
are not easily detected.
Embrittles some metals (high strength and low
alloy steel, nickel and titanium alloys are most
susceptible)
2
Hydrogen Gas Explosion




UEL: 74.2 % (V)
LEL: 4 % (V)
Burns with invisible/ colourless flame
Highly combustible in a wide range of fuelair mixtures and “auto-ignites” with low
ignition energy
Small molecule gives greater permeability
through solids than other gasses. Can leak
through materials and joints usually considered
gas-tight.
Sudden releases of compressed gas into air have
been a cause of past fire incidents.
Existing controls & measures



Worker and
others in the lab



Use smallest size cylinder that is workable to minimise
risks.
Gas rapidly rises; use in a well ventilated area, e.g.,
fume cupboard, to prevent any pockets of gas forming
Only use equipment (e.g., regulator, connectors and
pipework) designed for use with hydrogen gas, the
correct hoses must be used to resist permeation
Use flash-back arrestors (flame arrestor) with
hydrogen cylinders
Check set-up regularly for any leaks:
o The meter on the regulator should indicate
whether the cylinder is leaking if the contents of
the cylinder are dropping more rapidly that they
should be.
o A meter should be used regularly to detect if the
cylinder is leaking.
The gas cylinder must not be placed near any heat
sources or flames.
The gas will only be used for its intended purpose in
the reaction, which must have been COSHH assessed.
The cylinder must be handled properly – it is unlikely
that the cylinder will explode if the proper procedures
in the storage and use risk assessment are followed.
Risk rating
(a x b)
Persons
affected
and how
Likelihood
(b)
Hazard(s) identified
Severity
(a)
#
4
2
8
Additional
controls
required
Gasses should preferably be piped to the point of use from outside the building, eliminating the need to house cylinders in the labs. However, this is not
always possible or practical. If the cylinder is to be used in a lab, it should be kept in the external gas store until required and returned when no longer in
regular use.
UOB Risk Assessment
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University Health, Safety & Environment Service
Disposal
Cylinders are rented through the University suppliers (currently BOC). Empty cylinders are returned via Stores. “Empty” cylinders still retain a small volume of
gas, so must be treated with the same caution as full cylinders.
Empty cylinders should be stored apart from full cylinders, preferably with some indication of status (e.g. hang-on neck tag/ label)
Emergency Procedures
Leaking gas
Shut off the cylinder at the valve if possible. If it is not possible to shut off the gas supply, phone the emergency number (x666) and let them know the
problem. You may also need to evacuate the lab and building.
If the cylinder has been successfully closed so it is no longer leaking, contact the Technical Team (Marianne Harkins, Ewan Basterfield, Robyn Bott) as soon as
possible, and do not use the cylinder again until the problem has been rectified.
If the experiment is supplied directly from the cylinder, stop the work until the leak is found and rectified.
Fire from Leaking Gas
Do not extinguish unless leak can be stopped safely. Sound the fire alarm and evacuate the building. Phone the emergency number and let them know the
problem.
Additional Information
Definitions:
UEL - Upper Explosive Limit. Lowest concentration of gas in air at a given pressure and temperature that will propagate a flame when exposed to an ignition
source.
LEL - Lower Explosive Limit. Maximum concentration of gas in air at a given pressure and temperature in which a flame can be propagated.
Flashback Arrestors:
Available from BOC via Stores.
 BOC Resettable Flashback Arrestor, ref. 41540. Max 5.0 bar. £102.34
 Ryval Resettable Flashback Arrestor, ref. RY02040002. Max 4.0 bar. £66.25
 Single Use BOC Inline Flashback Arrestor, ref. 41542. Max 3.0 bar. £28.16
“Single use” means that if a flashback event occurred, a replacement device will be required.
UOB Risk Assessment
Template 2015v1
University Health, Safety & Environment Service