Health and Safety
Executive
Fuel cells
Understand the hazards, control the risks
This is a free-to-download, web-friendly version of HSG243
(First edition, published 2004). This version has been adapted for online use
from HSE’s current printed version.
You can buy the book at www.hsebooks.co.uk and most good bookshops. ISBN 978 0 7176 2766 0
Price £8.50
This book provides an introduction to the hazards associated with fuel cells and
the fuels that they use. It gives simple, straightforward technical advice to make
designers and users more aware of the hazards and the techniques available to
control the risks from this rapidly developing technology. It also provides guidance
to enable everyone working on ‘hydrogen economy’ projects to be more aware of
their responsibility to protect people, and should help to prevent an incident that
could jeopardise the acceptance of these new technologies.
HSE Books
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Health and Safety
Executive
© Crown copyright 2004
First published 2004
ISBN 978 0 7176 2766 0
All rights reserved. No part of this publication may be reproduced, stored in
a retrieval system, or transmitted in any form or by any means (electronic,
mechanical, photocopying, recording or otherwise) without the prior written
permission of the copyright owner.
Applications for reproduction should be made in writing to: The Office of Public Sector Information, Information Policy Team, Kew, Richmond, Surrey TW9 4DU or e-mail: [email protected]
This guidance is issued by the Health and Safety Executive. Following the guidance
is not compulsory and you are free to take other action. But if you do follow the
guidance you will normally be doing enough to comply with the law. Health and
safety inspectors seek to secure compliance with the law and may refer to this
guidance as illustrating good practice.
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Contents
Introduction 4
How fuel cells work 5
Types of fuel cell 5
Hazards associated with fuel cell installations 8
Fire and explosion hazards 8
Electrical hazards 12
Controlling the risk from fire and explosion 13
Avoiding flammable mixtures 13
Avoiding ignition sources 18
Controlling the risk from exposure to harmful chemicals 21
General safety considerations 22
Manual handling 22
Training 22
Emergency procedures 22
Legal requirements 23
General legislation 23
Legislation dealing with the fire and explosion hazards of fuel cells 23
Legislation dealing with the installation and maintenance of fuel cells 24
Appendix 1: Fuel cell types and electrochemistry 26
Appendix 2: Minimum separation distances 27
Glossary 28
References 30
Further information 32
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Introduction
1 Since the start of the new millennium, interest and activity in hydrogen and fuel cell technology has been accelerating rapidly. Though the invention of the fuel cell
can be traced back to work carried out in 1839 by William Grove, it was the work
done by NASA that really established its potential.
2 The use of fuel cells to provide the in-flight electrical power for the Apollo
spacecraft in the 1960s initiated global industrial research and development
programmes. Fuel cell technology has now reached a point where these devices
can be considered viable options for many applications, including combined heat
and power sources, back-up power supplies, remote location electricity provision
etc.
3 The potential for pollution-free transport through the use of fuel cells has
excited people for many years. It now seems likely that fuel cell-powered buses
and, ultimately, cars will be a feature of urban transport in the foreseeable future.
4 The purpose of this guidance is to provide an introduction to the hazards associated with fuel cells and the fuels that they use. It gives simple,
straightforward advice to help designers and users become more aware of the
hazards and understand how the risks from this rapidly developing technology
can be minimised. Everyone working on ‘hydrogen economy’ projects should be
aware of their responsibility to protect people and prevent an incident that could
jeopardise the acceptance of these new technologies.
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How fuel cells work
5 A fuel cell is a device for harnessing the energy liberated when hydrogen, or a
hydrogen-rich fuel, reacts with oxygen to produce water. Normally, when hydrogen
and oxygen react, a flame and heat energy are produced. In a fuel cell a flame is
not produced; the reaction produces only electricity and heat.
Hydrogen + oxygen Hydrogen + oxygen g water + electricity + heat
fuel cell combustion
g water + heat
6 In some ways a fuel cell is similar to a battery. Both are electrochemical devices
in which an electric current is produced from chemical reactions that take place at
the electrodes. A battery, however, stores electricity and needs regular recharging
or replacement, while a fuel cell continues producing electricity as long as it is
supplied with fuel.
7 A single fuel cell consists of an electrolyte sandwiched between two thin porous
electrodes - the anode and the cathode. The anode of the cell is usually coated
with a special catalyst which splits each hydrogen molecule into two protons (H+ ions) and two negatively charged electrons. The electrons leave the anode
and provide the electrical current in the external circuit to which the fuel cell is
connected. Oxygen, usually from air, is fed to the cathode of the cell where it
reacts with protons and the electrons returning from the external circuit, to produce
water.
Types of fuel cell
8 Although the reaction between hydrogen and oxygen is the basis of almost all
fuel cells, the manner in which this reaction is harnessed varies considerably. The
way the cell works is heavily dependent upon the nature of the electrolyte. The
characteristics and half-cell reactions of the most common types of fuel cell are
summarised in Appendix 1.
9 Fuel cells can be loosely grouped into those with acidic electrolytes, those
where the electrolyte is alkaline, and those that operate at high temperatures.
Acidic electrolyte fuel cells: PEMFCs and PAFCs
10 Successful examples of acidic electrolyte fuel cells are the proton exchange
membrane or polymer electrolyte membrane (PEM) and the phosphoric acid (PAFC)
fuel cell. In both of these cells the protons produced at the anode move through
the electrolyte to the cathode where water is produced from their reaction with
oxygen and the returning electrons.
11 The electrolyte in the PEM cell is a special fluorocarbon polymer that is
impervious to hydrogen gas and electrons but will readily allow the passage of
protons from the anode to the cathode. In the PAFC the electrolyte is a thin film
of phosphoric acid held in a fluorocarbon-bonded matrix. The electrodes of both
PEM and PAFC units are usually made from porous carbon impregnated with
platinum. In both of these devices the electrolyte is no thicker than a few sheets of
paper, allowing a large number of cells to be arranged in series to produce a cell
stack.
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12 PEM and PAFC devices are compact and can generate quite a lot of power
from a relatively small unit. PEM cells are currently being used in large transport
vehicles such as buses and traction units. PAFC units are often assembled into
very large stacks and a great many PAFC assemblies with electrical power outputs
in excess of 200 kW are in use around the world for stationary power generation.
The high tolerance of these units to impurities such as carbon monoxide and
carbon dioxide enables them to be run on hydrogen generated from natural gas or
other hydrocarbons using a reformer.
Alkaline electrolyte fuel cells: AFCs
13 These cells often use an aqueous solution of potassium hydroxide as the
electrolyte and operate at quite high temperatures, 100–250ºC. This allows them
to use non-precious metal catalysts at the electrodes. However, these potential
advantages are offset by the need for very high-purity hydrogen feed. Trace
amounts of carbon dioxide react with the electrolyte and cause irreparable damage
to the cell.
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14 AFCs differ considerably in the way in which they generate electricity. Oxygen,
from air supplied to the cell, reacts with water at the cathode of the cell, producing
hydroxide ions. These move towards the anode where their catalysed reaction
with hydrogen produces water and liberates electrons into the external circuit.
Consequently, in these cells water is produced at the anode rather than the
cathode, as is the case with other fuel cells.
High-temperature fuel cells: MCFCs and SOFCs
15 Molten carbonate fuel cells (MCFCs) operate at temperatures around 650ºC
and use a molten metal carbonate suspended in a porous ceramic matrix for the
electrolyte. At the cathode, oxygen and carbon dioxide are converted to carbonate
ions, which then move through the electrolyte to the anode and react with
hydrogen to produce carbon dioxide and water.
16 The high operating temperature of these cells enables less expensive catalysts
to be used and they do not require a separate reformer. Suitable hydrocarbon fuels
can be fed directly into the cell where internal reforming to hydrogen takes place.
Molten carbonate fuel cells are not damaged by the presence of carbon dioxide in
the feed gases, allowing a wide range of fuels to be used.
17 Solid oxide fuel cells (SOFCs) use a hard, non-porous ceramic material as the
electrolyte. The very high operating temperature, around 1000ºC, enables these
cells to carry out internal reforming of suitable hydrocarbon fuels and the use
of less expensive catalysts. SOFCs have quite good resistance to poisoning by
sulphur or carbon monoxide, enabling a wide range of fuels to be used.
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Hazards associated with fuel cell
installations
18 This section discusses the hazards of the substances and technology
associated with fuel cells. Everyone involved in the design, installation, use and
maintenance of fuel cells should have an appropriate understanding of these
hazards. Without this knowledge it is not possible to carry out a suitable risk
assessment.
19 In many situations the major hazards associated with a fuel cell installation may
be put into the following categories:
n dangerous substances:1
– fire and explosion;
– harmful effects of exposure;
n electric shock;
n general safety hazards, for example manual handling.
20 This guidance concentrates on controlling the risk from fire and explosion,
particularly when hydrogen is the fuel. General guidance describing how risk in
the workplace from the other significant hazards should be controlled is already
available.2
Fire and explosion hazards
Fuels
21 All the fuels suitable for use in cells readily catch fire and so present a
significant fire and explosion hazard. Materials such as these are called ‘dangerous
substances’ under the Dangerous Substances and Explosive Atmospheres
Regulations 2002 (DSEAR).1 These Regulations introduce new duties which include
avoiding sources of ignition and the release of dangerous substances into the
workplace.
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22 DSEAR also reinforces the general requirement for employers under the
Management of Health and Safety at Work Regulations 1999 to identify the
significant hazards present in the workplace and to carry out a suitable and
sufficient assessment of the risk from those hazards.2 Appropriate measures must
then be taken to reduce those risks to an acceptable level that is as low as
is reasonably practicable.
23 All fuels, such as hydrogen, petrol, methane, LPG etc, will catch fire and may
produce an explosion. Before an explosion can occur, a flammable mixture of the
fuel and air must form and a source of ignition must be present to ignite it.
24 Petrol and methane are fuels routinely used by millions of people every day.
Most users are aware of the properties of these fuels and what needs to be done
to handle them safely. The properties of hydrogen are often not widely appreciated
and this can result in the risk not being properly controlled.
25 The hazards of hydrogen are discussed in some detail below, followed by a
brief summary of the important different or additional hazards of other fuels. Some
of the ways in which sources of ignition, the other requirement for an explosion,
may be avoided are discussed later (see paragraphs 82–90).
Hazardous properties of hydrogen and its storage
26 Hydrogen has some unusual properties. If these are not appreciated and
appropriate measures not taken, then the likelihood of hydrogen escaping and a
fire or explosion occurring may be greater than with many other fuels. Some of the
important properties of hydrogen that may contribute towards this are:
n
n
n
n
n
n
n
n
very wide flammability range;
very low ignition energy;
possibility of detonation;
low viscosity;
high diffusivity;
very much lighter than air;
causes the embrittlement of some metals;
condensation of oxygen-rich liquid air on cryogenic storage systems.
27 Hydrogen is a gas that catches fire very easily. It burns with a flame that
is almost invisible and readily forms an explosive mixture with air. The range of
hydrogen/air concentrations that will explode is extremely wide, much wider than
almost any other fuel. Mixtures containing from as little as 4% v/v hydrogen, which
is the lower explosion limit (LEL), up to as much as 75% v/v, the upper explosion
limit (UEL), will readily ignite and explode.3
28 If a flammable mixture of hydrogen and air is allowed to form, the likelihood of
an explosion occurring is very high. This is because the energy necessary to initiate
a hydrogen/air explosion is very small. The ignition energy for a 2:1 hydrogen/
oxygen mixture is only about 0.02 mJ. This is less than one tenth that of other
common fuels such as methane, LPG or petrol. Even very small sparks, such
as those produced by wearing certain types of clothing, are capable of igniting
hydrogen/air mixtures and causing an explosion.4
29 A significant difference between hydrogen and other common flammable
fuels is that for the bulk (18–69% v/v hydrogen) of its flammable range there is a
possibility that a hydrogen/air mixture in a confined and heavily congested situation
may detonate.4,5
30 Detonations cause much more damage and are far more dangerous than
ordinary explosions (deflagrations). Consequently, the risk from detonation should
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always be considered in the risk assessment of systems handling or storing
hydrogen.
31 Hydrogen gas has a very low viscosity and so it is very difficult to prevent
hydrogen systems from developing leaks. Pipework that was ‘leak-tight’ when
pressure-tested with nitrogen will often be found to leak profusely when used
on hydrogen duty. This property increases the likelihood of a flammable mixture
forming.
32 Hydrogen is very much lighter than air, much more so than natural gas
(methane), and is also very diffusive. When it escapes it moves upwards very
rapidly. If a leak occurs in an open or well-ventilated area its diffusivity and
buoyancy will help to reduce the likelihood of a flammable mixture forming in the
vicinity of the leak.
33 However, when leaks occur within poorly ventilated or enclosed areas, the
concentration of hydrogen in the higher regions may rapidly reach dangerous
levels. If unprotected electrical equipment or other sources of ignition are present,
the risk from explosion will be considerable.
34 Almost all hydrogen is currently stored in high-pressure cylinders. The
cryogenic storage of liquid hydrogen for fuel cell use may, however, become more
widespread in the future. The hazards from the very low storage temperatures
used for liquid hydrogen, around -250ºC, include severe cold-burns and the
condensation of oxygen-enriched liquid air on unprotected pipework.
35 Liquid hydrogen boils at -253ºC at atmospheric pressure and so hydrogen
leaking from cryogenic storage will be very cold and may be heavier than air. As
a result, leaking gas will often sink initially, forming a flammable atmosphere at
low level, before warming up, becoming buoyant and rising. This is in marked
contrast to a leak of compressed hydrogen where the accumulation of a flammable
concentration of hydrogen is always at high level.
36 Research and development work on the storage of hydrogen in metal hydrides
has been in progress for many years. There are two main types of hydride storage
system. ‘Traditional hydrides’ use the reversible absorption of hydrogen into the
molecular lattice of transition metals.6 The finely divided metal is contained inside a
pressure vessel and is often a flammable or pyrophoric solid.
37 ‘Complex hydrides’ store hydrogen through reversible reactions involving
sodium aluminium hydride and similar materials.7 These materials are flammable
solids that also react vigorously with water to produce hydrogen and a corrosive
aqueous solution.
38 The pressure of hydrogen in these types of storage system depends on
storage temperature and the state of charge/discharge, but may often be in excess
of 10 barg.
The hazards of fuels other than hydrogen
39 Many cells use hydrogen produced from hydrocarbon fuels using reformer-type
technology located near the fuel cell stack. Some high-temperature fuel cells are
able to run on suitable hydrocarbon fuels without a separate reformer.
40 The reactions that take place within the reformer, or within high-temperature
fuel cells, convert the hydrocarbon fuel into hydrogen for use in the cell and carbon
dioxide, which is vented. Use appropriate measures, such as containment and
ventilation, to ensure that the carbon dioxide effluent stream from larger cells is
effectively discharged and does not produce an asphyxiation risk.
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41 Natural gas (methane) is lighter than air and will tend to diffuse upwards,
though much more slowly than hydrogen. The explosion limits for natural gas
(5–15% v/v) are also much narrower than those for hydrogen.8 Consider the
characteristics of both fuels fully when designing and operating dual fuel systems.
The pipework and equipment used to supply natural gas to the fuel cell should be
suitable and be designed to an appropriate standard.9
42 LPG vapour is considerably heavier than air, especially when cold, for example
when taken directly from a liquid storage vessel. In the event of a leak, LPG
vapour will usually percolate downwards and may accumulate on the floor or in
low-lying sumps, rapidly producing a flammable atmosphere. Mixtures containing
2–10% v/v LPG in air will readily ignite and explode.10 The significant differences
in the buoyancy and dispersion characteristics of the two fuels should be carefully
considered in systems where LPG and hydrogen may both be present. The
pipework and equipment used to store and supply LPG to the fuel cell should be
suitable and be designed to an appropriate standard.9
43 Methanol can be used directly by some types of fuel cell. This fuel has some
hazards that demand particular attention. In addition to being a highly flammable
liquid, methanol is also toxic by inhalation, ingestion and, notably, by skin
absorption.11 Appropriate precautions such as containment and ventilation should
be taken to prevent spillages and the accumulation of hazardous methanol/air
mixtures whenever it is used.
44 Ignition sources should be avoided through the measures described later (see
paragraphs 82–90) where there is the potential for flammable methanol/air mixtures
to form.12, 13 More detailed advice on these issues is contained in Safe use and
handling of flammable liquids.14
Sources of ignition
45 A flammable fuel/air mixture will not explode unless it is exposed to a sufficiently
powerful ignition source. Common sources of ignition include:
n
n
n
n
n
naked flames and sparks from welding, burning or grinding;
electrostatic sparks from poorly earthed or non-conductive pipework;
electrical sparks from motors, switches, relays or mobile phones;
sparks from mechanical impacts;
hot surfaces, for example bearings.
46 Further guidance on sources of ignition may be found in Safe use and handling
of flammable liquids.14
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Electrical hazards
47 Electric shock can be a life-threatening hazard and must not be overlooked
in the design, operation and maintenance of the fuel cell and its associated
equipment.15
48 Electrical hazards usually arise from two distinct areas within fuel cell
installations - the normal 240 or 415 volt mains a.c. supply into the area and the
d.c. electrical output of the fuel cell stack. With larger units there may be a third
area - the a.c. output of an inverter connected to the fuel cell.
49 The voltage and current produced by each element in the stack is usually quite
small; however, the total output from the stack may be of the order of 200–400
volts and large electrical currents are often available. The electrical output from
quite modest fuel cells can be life threatening.
50 Large fuel cell stacks may also provide large currents as well as lethal voltages. If a metal object is inadvertently placed across the output busbars of such a cell
then a ‘short circuit’ will be produced and a large electrical current will flow through
the object. This is likely to get hot very quickly and may produce a shower of
sparks.
51 The electrical equipment associated with the fuel cell should be designed and
installed to an appropriate standard, and suitable arrangements should be in place
to ensure that only competent personnel are able to gain access to the equipment.
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Controlling the risk from fire and
explosion
52 Consider the following approaches when developing the strategy to minimise
the risk from fire and explosion:
n
n
n
n
investigate the replacement of hydrogen with a less hazardous fuel;
avoid the formation of flammable mixtures;
avoid sources of ignition;
use suppression, containment or mitigation of the explosion.
53 In many situations avoiding flammable atmospheres and sources of ignition will
be the most useful approach.
Avoiding flammable mixtures
54 The likelihood of a flammable atmosphere being produced may be reduced
using the following techniques:
n
n
n
n
containment;
segregation;
separation;
ventilation.
Containment
55 Measures to prevent the release of dangerous substances should be given the
highest priority. If you can prevent a release, a flammable atmosphere cannot form
and the risk from explosion is eliminated.
56 Minimise the likelihood of a leak occurring by using high-quality engineering. Pay particular attention to the design, operation and maintenance of the hydrogenhandling equipment. In this way the likelihood and size of any potential leak can be
minimised, leading to a greatly reduced risk from explosion.5 By considering the
guidance below you will be following good practice:
n ensure that the storage equipment, pipework and connections conform to n
n
n
n
n
n
n
n
n
an approved standard for hydrogen equipment;3
ensure that maintenance work is effectively controlled and is only carried out by authorised competent people;
minimise the frequency with which connections are made and broken;
use appropriate refillable stationary storage rather than regularly replacing large numbers of separately connected cylinders;
use the minimum length and size of pipework that is appropriate;
minimise the number of joints by using continuous lengths of pipework wherever practicable;
use fusion jointing (welding or brazing) or flanged/threaded connectors to join pipework;
ensure that the system is leak-tested before use in a manner appropriate for hydrogen systems;3
carry out appropriate inspections of the system at suitable regular intervals and record the results;
review the operation and maintenance history at suitable intervals.
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57 When high-pressure storage is used it should be designed and built to an
appropriate design code or standard and located in a secure open-air compound.3
The measures used to prevent unauthorised access, vandalism and impact from
vehicles should be appropriate to the location.
58 Indoor storage of compressed hydrogen is not recommended. It may be
permissible in single-storey, purpose-designed buildings, provided appropriate
safety measures, such as effective ventilation, fire-resistant construction and
explosion relief are taken and the risks have been reduced as low as is reasonably
practicable.3 In most situations, however, indoor storage should usually be
considered inappropriate if an outdoor location is practicable.
59 Cryogenic hydrogen storage installations should be constructed to an
appropriate code and located in a suitable open-air position and not within an
occupied building.16 Low-temperature storage installations should incorporate
suitable measures to prevent oxygen-rich liquid air, a powerful oxidising agent, from
condensing on uninsulated surfaces exposed to liquid hydrogen temperatures.16
To avoid the risk from fire, potentially flammable materials, including asphalt and
tarmac, should not be present beneath pipework where condensation may occur.
60 Use only appropriate pipework and fittings for the supply of hydrogen.3, 17
Cupro-nickel and stainless steel are preferred materials for high-pressure pipework
whereas copper can be used for lower pressures. All pipework joints should be
brazed or welded. Flanged or screwed joints are acceptable but avoid using them if
possible.
61 Compression joints are generally not recommended for use on hydrogen
systems as it is difficult to achieve and maintain these in a ‘leak-free’ condition. Where their use is considered essential, such as on small-bore pipework,
they should be suitable for the duty and used in strict accordance with the
manufacturer’s instructions.
Segregation and separation
62 Arranging the component parts of an installation in an appropriate way can
significantly reduce the likelihood of an explosion. The risk from explosion will
usually be much lower when the hydrogen-handling equipment is well separated
from electrical equipment or other ignition sources.
63 Always take into account the tendency of hydrogen to migrate rapidly upwards.
Its buoyancy should be fully considered and used to reduce the risk from fire and
explosion when designing or arranging the components of a fuel cell or installation.
This can be done through the following measures:
n segregate and physically separate equipment for handling hydrogen from foreseeable sources of ignition;
n separate the hydrogen storage area from the fuel cell and the fuel cell from equipment using its electrical output;
n locate any potential sources of ignition well below any equipment from which hydrogen may leak;
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8
n avoid locating potential sources of ignition, such as non-flameproof electrical
light fittings, immediately below horizontal bulkheads or impervious ceilings
under which hydrogen may accumulate;
n ensure that any area, enclosure or housing etc, into which hydrogen may
leak, is designed to prevent the gas becoming trapped and is equipped with
effective high- and low-level ventilation;
4
8
n do not locate systems using or storing hydrogen beneath unprotected electrical
equipment or high-voltage power lines;3
n use gas-tight compartments or bulkheads and ventilation to reduce the
likelihood of leaking hydrogen reaching potential sources of ignition.
Separation distances
64 Recommended separation distances are the minimum distances considered
necessary to mitigate the effects of likely foreseeable events and prevent a minor
incident escalating into a major one.18 They are used to separate different hazards,
such as high-pressure hydrogen storage from an ignition source, or a hazard from
vulnerable objects or people.
65 The recommended distances are intended to give people and equipment a
suitable degree of protection from a foreseeable event on the installation, such as
a hydrogen leak and subsequent jet fire. The separation that they provide should
ensure that the risk to people from heat radiation or from flame impingement onto
other flammable materials is low. Separation distances are also calculated to give
protection to the installation from off-site events such as impact from vehicles or
machinery, releases of flammable materials, uncontrolled ignition sources or the
radiant effects of off-site fires etc.
66 The use of established separation distances around equipment handling or
storing hydrogen or other dangerous substances has traditionally been considered
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a fundamental requirement for the design of a safe installation. You should measure
the horizontal separation distances required from those points in the system where,
in the course of operation, an escape of hydrogen may occur. Consult the most
recent version of an appropriate code for additional information on the appropriate
use of separation distances.
67 In circumstances where it is not practicable to use the minimum separation
distances summarised in Appendix 2, an acceptable situation may be achieved
through the use of suitable fire-resistant barriers or other risk reduction techniques.3
68 There may be situations where the recommended distances are considered
inappropriate, for example when the operating pressure of the system is low.
Where the recommended separation distances are not employed, the onus is
on the dutyholder to demonstrate through a suitable assessment that the risk is
acceptable and has been reduced as low as is reasonably practicable.
Ventilation
69 Ventilation is a very effective way of lowering the risk from explosion. When the
concentration of fuel in a fuel/air mixture is reduced below the lower explosion limit
(LEL) an explosion cannot occur.
70 DSEAR1 requires employers to provide adequate ventilation to ensure that
any foreseeable release of a dangerous substance does not accumulate to a
concentration that affects the safety of people. Use the following principles to
ensure that effective ventilation is provided:
n
n
n
n
n
n
n
locate hydrogen storage/handling equipment outside;
estimate the maximum foreseeable leak rate;
provide adequate high and low ventilation;
beware of low ceilings, canopies, covers and roofs;
ensure the dilution air is drawn from a safe place;
ensure vents and purges discharge to a safe place;
use computational fluid dynamics (CFD) for complex ventilation requirements.
71 Those parts of the fuel cell installation that handle hydrogen or other dangerous
substances should be located in the open air. Where this is not done, the onus is
on the dutyholder to justify that it was not reasonably practicable to use an outdoor
location and that the risk from the equipment in the chosen location is acceptable.
72 When using an outdoor location for hydrogen storage it is still essential to
ensure that efficient dilution of any leakage will take place. Follow the guidelines
below when designing outdoor storage and supply systems to ensure that the
likelihood of a flammable atmosphere accumulating is minimised:
n
n
n
n
avoid the use of low, impervious roofs, canopies or bulkheads;
avoid locations below eaves or other overhanging structures;
use a suitable, non-combustible security fence rather than a wall;
ensure adequate high- and low-level ventilation apertures where a wall around
the storage system is unavoidable.
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8
73 Whenever hydrogen is used or stored in an enclosed or partially enclosed
area, effective ventilation must be used to prevent the formation of an explosive
atmosphere. The size of any foreseeable leak into the area should be estimated
and used as a basis for calculating the ventilation requirements. These should be
sufficient to ensure that the concentration of hydrogen inside any occupied area
is normally maintained below 10% LEL with occasional temporary increases up to
25% LEL. Inside an unoccupied enclosure, fuel cell housing or compartment, the
ventilation should ensure that the concentration cannot exceed 1.0% v/v (25% LEL).
74 In situations where effective monitoring of the hydrogen concentration is
provided and interlocked into a suitable shutdown system it may be acceptable to
operate cabinets and housing at up to 2% v/v hydrogen. Consult relevant guidance
to ensure that the alarm/shutdown arrangements are suitable for the installation.19
4
8
75 Use appropriate mechanical means whenever natural ventilation cannot provide
the necessary dilution. In these situations a suitable monitoring and shutdown
system should ensure that the supply of hydrogen to the area is safely isolated in
the event of a failure of the ventilation equipment or when a build-up of hydrogen is
detected.
76 The design of any mechanical ventilation system must not involve the location
of the fan motor within a potentially explosive air stream. Position ventilation fans
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near the air inlet and use them to force clean air through the enclosure. Do not site
them near the outlet or use them to draw potentially contaminated air through the
system.
77 The cooling/air-supply fan or compressor present in many fuel cell modules
may sometimes be suitable to provide effective ventilation. Where this approach
is used, the air must be drawn from a safe place and the direction of the forced
airflow should be compatible with the expected movement of any hydrogen release
as a result of buoyancy, thermal effects etc.
78 The tendency for hydrogen to rise from leaks and accumulate against
impervious ceilings and high-level bulkheads has been identified previously as a
significant hazard. The location and type of electrical equipment used in areas
where hydrogen may be present and the design of ventilation arrangements should
recognise this hazard and be appropriate.
79 Internal partitions and bulkheads may be used effectively to separate ignition
sources from potential sites of hydrogen leakage. Differential pressurisation of
separate compartments may be used to prevent the ingress of hydrogen into areas
containing sources of ignition. Where this technique is used, the pressurisation air
should be drawn from and discharged to a safe place. Install an appropriate alarm/
shutdown system to detect and respond to any loss of ventilation or differential
pressure.
80 The dilution airflow and the number and location of flammable atmosphere
detectors should be appropriate in complex systems or congested locations. An
appropriate modelling technique should be used in these situations to ensure that
pockets of flammable mixture will not accumulate and remain undetected.
81 In situations where other fuels such as methane, LPG etc are present, in
addition to hydrogen, take into account their different densities and diffusivities to
ensure that the ventilation arrangements provided are appropriate.
Avoiding ignition sources
82 A flammable mixture will not explode if a source of ignition is absent. Although
it is extremely difficult to eliminate all sources of ignition, avoiding ignition sources
should be an important part of your overall risk reduction strategy. It must be used
in all areas where a potentially explosive atmosphere may be present. The following
techniques should be included in your approach to avoiding ignition sources:
n
n
n
n
n
n
n
n
carry out a hazardous area assessment;
identify the nature and extent of hazardous zones;
use suitable signs to denote the boundaries of hazardous zones;
locate electrical equipment in non-hazardous areas;
use appropriately classified equipment in hazardous areas;
use continuity bonding, earthing and anti-static clothing to avoid static;
control hot work, vehicles, smoking and the use of mobile phones;
provide lightning protection where appropriate.
83 When planning a fuel cell project it is important to consider whether it will
introduce new fire and explosion hazards into an area where previously these were
absent or whether the proposed location is already a hazardous area. In other
words, does the need to control ignition sources result from the possibility of a
hydrogen leak from the new fuel cell installation or does the fuel cell represent the
introduction of a potential source of ignition into an existing hazardous area?
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84 Where a potentially explosive atmosphere may be present in the workplace,
DSEAR1 requires employers to assess and identify those areas in which ignition
sources need to be controlled. The areas where explosive atmospheres could be
formed must be identified and designated as hazardous zones according to the
principles of Hazardous Area Classification.12, 13
85 The results from the classification exercise should be used to ensure that the
appropriate category of equipment is used in the fuel cell installation and that only
suitable equipment is present in the vicinity of the new installation.
86 For situations where hydrogen and/or other flammable gases or liquids may be
present, the following classifications should be used where appropriate:
n Zone 0: An area in which an explosive atmosphere is present continuously or
for long periods. Only category 1 equipment should be used in these areas;
n Zone 1: An area where an explosive atmosphere is likely to occur during normal
operation. Only category 1 or 2 equipment should be used in these areas;
n Zone 2: An area where an explosive atmosphere is not likely to occur during
normal operation and, if it does occur, is likely to do so infrequently and will
only last for a short period. Only category 1, 2 or 3 equipment should be used
in these areas.
87 Electrical equipment appropriate for use in the different areas of the workplace
should be determined once the hazardous areas have been identified and
classified.12, 13 When selecting electrical equipment for use in hazardous areas,
specify the temperature class and the apparatus group appropriate for the type of
flammable atmosphere likely to be present.
88 You should use the results of the hazardous area classification exercise to
ensure that suitable controls are placed on all other foreseeable ignition sources.
These should include hot work, smoking, vehicles, mechanical equipment, mobile
phones and work clothing.
89 It is important not to overlook the fuel cell itself when ensuring that only suitable
equipment is present in hazardous areas. When designing and constructing the fuel
cell you should consider the following points:
n ensure that any fuel cell likely to be used where a potentially explosive
n
n
n
n
n
n
atmosphere may be present, ie a hazardous area, complies with the ATEX (EC
Directive 94/9/EC) Regulations and BS EN 60079;20, 12
ensure that the electrical components, connectors, materials etc employed are suitable for their intended use and environment;
locate the electrical/electronic components of the fuel cell below any
foreseeable sources of hydrogen leakage;
use suitable gas-tight barriers to separate electrical/electronic equipment from
areas where hydrogen may be present;
use appropriate ventilation to prevent the formation of potentially explosive
mixtures;
the use of explosion-resistant equipment or explosion relief may be appropriate
in certain situations;
use the guidance available in recognised standards such as IEC 62282 to avoid
basic design flaws.21
90 Static electricity sparks have often been the source of ignition in explosions
of flammable hydrogen/air mixtures. Effective arrangements should be in place to
prevent the build-up of static charges that may lead to an incendive discharge.
Consider suitable measures to reduce the risk from static electricity. These may
include:
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n ensuring that all pipework is conductive and has effective electrical continuity,
n
n
n
n
especially across mechanical joints such as flanges;
ensuring that all pipework and equipment is effectively earthed;
carrying out and documenting appropriate earthing/continuity checks;
wearing antistatic clothing and footwear in hazardous areas;
providing appropriate protection against the risk from lightning when designing
outdoor fuel cell or hydrogen storage facilities.3
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Controlling the risk from
exposure to harmful chemicals
91 Assess all the chemicals associated with the fuel cell to identify if any of
them pose a risk to health. Some fuel cells may contain harmful, corrosive or
irritant chemicals in their electrolytes. However, these chemicals are generally in a
closed system and pose no threat to health from exposure during normal use. No
additions to or replacement of the electrolyte are normally anticipated. There may
be some risk of exposure to these substances if the fuel cell becomes damaged or
during disposal. Have suitable procedures in place to safeguard personnel from the
harmful effects of specific chemicals and from the potential for such an exposure.
92 Methanol/air mixtures are hazardous to health as well as being potentially
explosive. Consequently, you should do a suitable and sufficient assessment of the
risk to health under the Control of Substances Hazardous to Health Regulations
(COSHH) and identify the steps that need to be taken to prevent or adequately
control exposure.22 To use methanol safely these risks must be taken into account
and suitable control measures incorporated into equipment and procedures.
93 The concentration of methanol in air considered to be harmful to health
(TWA 200ppm) is very much lower than one which is flammable (LEL 6% v/v).11
Consequently, for large enclosures which people may enter, the ventilation
arrangements etc should be appropriate to ensure that a harmful (to health)
atmosphere does not accumulate. These arrangements should easily ensure that
the risk of explosion is eliminated.
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General safety considerations
94 It is important not to forget the basic aspects of a safe system of work when
designing and operating in a high-technology environment. Manual handling,
training and emergency procedures are three aspects of safety management that
should not be overlooked.
Manual handling
95 Thoroughly assess the risks arising from manual-handling operations
associated with the use and maintenance of the fuel cell. In particular, the choice of
location and the mode of fuel storage (for example cylinders, refillable static storage
etc), ease of access and the equipment provided can have a significant impact on
the overall risk from the installation.
Training
96 Everyone who may be affected by the hazards associated with the fuel
cell installation should have been trained to an appropriate level. The operation
and maintenance of the fuel cell installation should be covered by established
documented procedures.
Emergency procedures
97 Documented procedures should be established to cover all foreseeable
emergency situations. Appropriate training on the required response to emergency
situations should then be given. During the planning stage of a fuel cell project it is
good practice to inform the fire brigade that hydrogen will shortly be stored at the
location.
98 It is likely that as the use of fuel cell technology accelerates, many applications
will involve installing equipment into existing workplace environments rather than
into new purpose-designed areas. The safe ‘retro-fitting’ of fuel cells into areas
with little prior experience of hydrogen, especially domestic environments, will raise
a multitude of new issues. Many of these issues may not have been examined
previously as they were not considered relevant or were of little significance in the
industrial environments in which hydrogen has historically been used.
99 These new hydrogen usage/storage situations will often present significant
technical and engineering challenges to dutyholders. One of the most significant
of these will be the very large demand for the technical skills necessary to ensure
that appropriate risk assessments are carried out. It is particularly important that
pressure to find solutions to technical or commercial problems does not result in
‘tunnel vision’ where safety is concerned.
100 The most important aspect of designing and operating a fuel cell installation is
to ensure that:
n the important hazards have been identified and appropriate measures
taken so that the risk presented by the fuel cell installation is
acceptable and has been reduced as low as is reasonably practicable.
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Legal requirements
101 There are two areas of health and safety legislation relevant to fuel cell
installations:
n those identifying general duties;
n those regulating particular features or technical aspects.
General legislation
102 Employers are required under the Health and Safety at Work etc Act 1974 to
secure the health, safety and welfare of people at work and to protect those not at
work from risks to their health and safety arising from work activities.
103 The Management of Health and Safety at Work Regulations 1999, often
referred to simply as the ‘Management Regulations’, require all employers and selfemployed people to assess the risks to workers and others so that they can decide
what measures need to be taken to fulfil their statutory duty.2
104 The general principles of an appropriate risk assessment are identified in
BS EN 1050: 1997 Safety of machinery. Principles of risk assessment23 and in
the Management Regulations. In the risk assessment process employers should
identify the potential hazards and determine their significance. They should then
take appropriate precautionary measures to reduce the risk from the hazards to an
acceptable level that is as low as is reasonably practicable.
105 The Provision and Use of Work Equipment Regulations 1998 (PUWER 98)
will apply to fuel cells in most work situations and impose duties to ensure that the
equipment provided is suitable and appropriate.24
Legislation dealing with the fire and explosion hazards of fuel cells
106 Employers and other dutyholders should ensure that the design, installation,
operation and maintenance of fuel cell installations complies with the requirements
of the Dangerous Substances and Explosive Atmospheres Regulations 2002
(DSEAR).1
107 DSEAR is a set of regulations concerned with the protection of people against
the risks from fire and explosion arising from the use or storage of dangerous
substances in the workplace. Dangerous substances include all those flammable
materials likely to be used as fuels for cells, for example hydrogen, methanol,
natural gas and LPG. Under DSEAR the risks from fire and explosion arising from
the use of dangerous substances must be assessed in an appropriate manner.
108 A risk assessment under DSEAR should include a careful identification and
examination of the dangerous substances present or likely to be present in the
workplace. It should consider which activities involve dangerous substances, and
how these activities might go wrong and produce a fire or explosion that could
harm employees or the public. The purpose of DSEAR is to help determine what
needs to be done to eliminate or reduce the safety risks arising from the use of
dangerous substances in the fuel cell system. The overall risk assessment should
take account of the hazards of the dangerous substances used and any other
hazards associated with the operation of the fuel cell, for example:
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n
n
n
n
n
n
n
the likelihood of hazardous explosive atmospheres occurring;
all potential ignition sources;
all foreseeable factors, including accidental damage and vandalism;
control of any non-routine operations;
maintenance and repair activities;
manual-handling issues;
human factors and training requirements.
109 Where five or more people are employed, the findings of the risk assessment
must be recorded and reviewed at a suitable frequency or when significant
changes occur in the workplace.
Legislation dealing with the installation and maintenance of
fuel cells
110 Fuel cells operating on hydrogen, methane, ethane or LPG may be classified
as gas appliances under the Gas Safety (Installation and Use) Regulations
1998 (GSIU Regulations).9, 25 These Regulations deal with the safe installation,
maintenance and use of gas systems, including gas fittings and appliances, mainly
in domestic and commercial situations. In most situations the principal function of
the fuel cell will be the production of electricity and not heat. Where electricity is
the primary output, irrespective of how the electrical energy is used, the fuel cell
appliance will not be covered by the Gas Appliance Directive 90/396/EEC (GAD).
111 Regulation 3 of the GSIU Regulations requires anyone carrying out work on a
gas fitting or storage vessel to be competent to do so. Self-employed people and
employers of people carrying out work on gas fittings and appliances in domestic
situations and non-industrial premises are required to belong to a class of persons
approved by the Health and Safety Executive. Currently, this means that only
members of the Council for Registered Gas Installers (CORGI) may carry out the
work in these situations.
112 The GSIU Regulations apply to fuel cells using methane, ethane or LPG in
domestic and commercial situations. The Regulations also cover fuel cells operating
on hydrogen that are located in domestic premises, but do not apply to hydrogen
cells in non-domestic premises such as commercial buildings, warehouses, offices
or factories.
113 Unless the premises are used for domestic, sleeping or accommodation
purposes or are hired out as part of a business, the GSIU Regulations do not apply
to fuel cells when they are located in factories, farms, construction sites, mines/
quarries, ships or vehicles.25 In these situations DSEAR will normally apply.
114 In summary:
n where a fuel cell operates on hydrogen in a domestic situation all installation
or repair work must be carried out by a (CORGI) registered installer who is
competent in the work being done;
n where a fuel cell operates on methane, ethane or LPG in a domestic situation
or in commercial premises all installation or repair work must be carried out by
a (CORGI) registered installer who is competent in the work being done;
n when a fuel cell is located in a factory all installation or repair work must
be carried out by a person competent to carry out that work. They do not
necessarily need to be registered with CORGI.
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115 The enforcing authority for the GSIU Regulations is HSE or the relevant local
authority as determined in the particular circumstances by the Health and Safety
(Enforcing Authority) Regulations 1998.26
116 In general, DSEAR and the GSIU Regulations do not cover fuel cells located
on vehicles operating on public roads. In most instances the Vehicle and Operator
Services Agency (DfT) will be the lead regulator in these situations.
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Appendix 1: Fuel cell types and
electrochemistry
Fuel cell type
Electrolyte
Operating
temperature
(ºC)
Electrode reactions
PEM: Proton exchange
membrane
Polymer electrolyte
membrane
Perfluorosulphonic acid polymer
60–100
Anode: 2H2 -> 4H+ + 4e-
DMFC: Direct methanol fuel
cell
Perfluorosulphonic acid polymer
60–100
Anode: 2CH3OH + 2H2O -> 2CO2 + 12H+ + 12eCathode: 12H+ + 3O2 + 12e- -> 6H2O
PAFC: Phosphoric acid fuel
cell
Liquid phosphoric acid soaked in a
matrix
175–100
Anode: 2H2 -> 4H+ + 4eCathode: O2 + 4H+ + 4e- -> 2H2O
AFC: Alkaline fuel cell
Aqueous potassium hydroxide
soaked in a matrix
90–100
Anode: 2H2 + 4OH- -> 4H2O + 4eCathode: O2 + 2H2O + 4e- -> 4OH-
MCFC: Molten carbonate
fuel cell
Molten lithium and sodium /
potassium carbonates in a matrix
600–1000
Anode: 2H2 + 2CO32- -> 2H2O + 4e- + 2CO2
Cathode: O2 + CO2 + 4e- -> 2CO32-
SOFC: Solid oxide fuel cell
Solid zirconium oxide with trace of
Yttria
600–1000
Anode: 2H2 + 2O2- -> 2H2O + 4eCathode: O2 + 4e- -> 2O2-
Cathode: O2 + 4H+ + 4e- -> 2H2O
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Appendix 2: MINIMUM
SEPARATION DISTANCES
Type of exposure
Distance from hydrogen
source (m)
1
Open flame, ignition source including uncertified electrical
equipment
5
2
site boundary, or areas where people congregate, such
as car parks
8
3
Building, wood frame construction
8
4
Wall openings in offices or workshops (installations
should not be directly below openings)
5
5
Bulk flammable liquids or LPG above ground
8
6
Bulk flammable liquids or LPG under ground
5
7
Flammable gas cylinder storage other than hydrogen
5
8
Oxygen cylinder storage
5
9
Liquid oxygen storage
8
10
Liquid nitrogen or argon storage
5
11
Stored combustible material, eg timber
8
12
Air compressor and ventilator intakes (installations should
not be directly below such intakes)
8
13
Activity other than that directly related to the hydrogen
installation
5
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Glossary
Anode: The electrode at which the oxidation reaction of the cell occurs. This
electrode accepts electrons from substances in the cell.
Catalyst: A substance that speeds up a chemical reaction but is not consumed in
the reaction.
Cathode: The electrode at which the reduction reaction of the cell occurs. This
electrode donates electrons to substances in the cell.
CFD: Computational fluid dynamics. The use of computer modelling to simulate
and predict the movement and concentration gradients of gases and liquids.
Cogeneration: The simultaneous production of electricity and heat from a power
source.
Dangerous substance: A substance or material which, because of its properties
or the way in which it is used, could cause harm to people.
DSEAR: The Dangerous Substances and Explosive Atmospheres Regulations
2002. Direct methanol fuel cell (DMFC): A fuel cell in which methanol is oxidised
directly at the anode without prior reforming to hydrogen.
Distributed generation: Small-scale power generation equipment that provides
electrical power at or much closer to the customer’s site than centrally located
large-scale power stations.
Electrode: A solid electrical conductor through which electricity enters or leaves
the cell.
Electrolyte: A non-metallic conductor in which the current is carried by the
movement of ions.
External reforming: Production of hydrogen from a hydrocarbon or other
hydrogen-rich fuel before entry into the fuel cell.
Fluorocarbon: Chemical compound composed almost entirely of the elements
carbon and fluorine.
Fuel: Substance used to generate heat or electrical power through a chemical
reaction such as combustion or electrochemistry.
Fuel cell: An electrochemical device that continuously converts the chemical
energy of a fuel and an oxidising agent into electrical energy. The fuel and oxidant
are stored outside the cell and are transferred to the cell as they are consumed.
Hazardous area/place: A place in which an explosive atmosphere may occur in
such quantities/frequencies as to require special precautions to protect the health
and safety of the workers concerned. Hydrocarbon: A chemical compound consisting of only the elements carbon and
hydrogen, for example methane, propane, butane etc.
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Incendive: Having sufficient energy to ignite a flammable mixture.
Ignition source: A source of energy, such as a spark or hot surface, that is likely
to cause a flammable mixture to catch fire.
Ion: An electrically charged atom or molecule.
Matrix: The supporting material into which the active materials are embedded.
Membrane: The separating layer in certain types of fuel cell (PEM and DMFC) that
acts as an electrolyte as well as a barrier film segregating the gases in the anode
and cathode compartments.
Oxidation: The loss of electrons from a substance. In a fuel cell this is the reaction
that generates the electric current.
Reformer: A catalytic device in which hydrocarbon fuels are converted into
hydrogen-rich fuel gases suitable for use in a fuel cell.
Unprotected electrical equipment: Electrical equipment which, because of its
design or manufacture, is not suitable for use in a potentially explosive atmosphere.
Ventilation: The supply of sufficient clean air to ensure that releases of dangerous
substances do not accumulate to a concentration that affects people’s health and
safety.
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References
1 Dangerous substances and explosive atmospheres. Dangerous Substances and Explosive Atmospheres Regulations 2002. Approved Code of Practice and guidance L138 HSE Books 2003 ISBN 0 7176 2202 7
2 Management of health and safety at work. Management of Health and Safety at Work Regulations 1999. Approved Code of Practice and guidance L21 (Second edition) HSE Books 2000 ISBN 0 7176 2488 9
3 Gaseous hydrogen stations IGC Doc 15/96 European Industrial Gases Association
4 Safety standard for hydrogen and hydrogen systems NSS 1740.16 1997 National Aeronautics and Space Administration 5 Basic considerations for the safety of hydrogen systems ISO/DPAS 15916 2001
6 Agreement on production and storage of hydrogen. Task 12: Metal hydrides and carbon for hydrogen storage: Final task report International Energy Agency
7 DK Slattery and MD Hamton ‘Complex hydrides for hydrogen storage’ Proceedings of 2002 hydrogen programme review US DoE
8 Essential gas safety (Third edition) 2003 CORGI Tel: 0870 516 8111
9 Safety in the installation and use of gas systems and appliances. Gas Safety (Installation and Use) Regulations 1998. Approved Code of Practice and guidance L56 (Second edition) HSE Books 1998 ISBN 0 7176 1635 5
10 Bulk LPG storage at fixed installations Code of practice 1 Liquefied Petroleum Gas Association 11 Lewis, RJ Sax’s dangerous properties of industrial materials (Tenth edition) J Wiley and Sons 2000 ISBN 0471 35407 4 12 BS EN 60079-10: 2003 Electrical apparatus for explosive gas atmospheres. Classification of hazardous areas and PD 60079-14: 2000 A guide to the application of BS EN 60079-14 British Standards Institution
13 Area classification code for installations handling flammable fluids. Model code of safe practice in the petroleum industry Part 15 Institute of Petroleum
ISBN 0 85293 223 5
14 Safe use and handling of flammable liquids HSG140 HSE Books1996
ISBN 0 7176 0967 7
15
16
17
Electricity at work: Safe working practices HSG85 (Second edition) 2003 HSE Books ISBN 0 7176 2164 2
Safety in storage, handling and distribution of liquid hydrogen Doc 06/02/E European Industrial Gases Association
Industrial gas cylinder manifolds and distribution pipework/pipelines (excluding acetylene) Code of Practice CP4 British Compressed Gases Association
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18
19
20
21
22
23
24
25
26
Determination of safety distances IGC Doc 75/01/E/rev European Industrial Gases Association
BS EN 50073: 1999 Guidelines for selection, installation, use and maintenance of apparatus for the detection and measurement of combustible gases or oxygen British Standards Institution
The Equipment and Protective Systems Intended for Use in Potentially Explosive Atmospheres Regulations 1996 SI 1996/192 The Stationery Office 1996 ISBN 0 11 053999 0
Fuel cell technologies. Part 2: Fuel cell modules Draft IEC 62282-2
COSHH essentials: Easy steps to control chemicals - Control of Substances Hazardous to Health Regulations HSG193 (Second edition) HSE Books 2003 ISBN 0 7176 2737 3
BS EN 1050: 1997 Safety of machinery. Principles for risk assessment
British Standards Institution
Safe use of work equipment. Provision and Use of Workplace Equipment Regulations 1998. Approved Code of Practice and guidance 1998 L22 1998
HSE Books ISBN 0 7176 1626 6
The Gas Safety (Installation and Use) Regulations SI 1998/2451
The Stationery Office 1998 ISBN 0 11 079655 1
The Health and Safety (Enforcing Authority) Regulations 1998 SI 1998/494
The Stationery Office ISBN 0 11 065642 3
While every effort has been made to ensure the accuracy of the references listed in
this publication, their future availability cannot be guaranteed.
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Further information
For information about health and safety ring HSE’s Infoline Tel: 0845 345 0055 Fax: 0845 408 9566 Textphone: 0845 408 9577 e-mail: [email protected] or
write to HSE Information Services, Caerphilly Business Park, Caerphilly CF83 3GG.
HSE priced and free publications can be viewed online or ordered from www.hse.gov.uk or contact HSE Books, PO Box 1999, Sudbury, Suffolk CO10 2WA Tel: 01787 881165 Fax: 01787 313995. HSE priced publications are also available from bookshops.
British Standards can be obtained in PDF or hard copy formats from the BSI online
shop: www.bsigroup.com/Shop or by contacting BSI Customer Services for hard
copies only Tel: 020 8996 9001 e-mail: [email protected].
The Stationery Office publications are available from The Stationery Office, PO Box 29, Norwich NR3 1GN Tel: 0870 600 5522 Fax: 0870 600 5533 e-mail: [email protected] Website: www.tso.co.uk (They are also
available from bookshops.) Statutory Instruments can be viewed free of charge at www.opsi.gov.uk.
Published by HSE 03/10
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