Introduction to Health and Safety at Work

13.9.5 Mitigation 
measures
Choose mitigation measures, which are consistent with 
the risk assessment and appropriate to the nature of the 
activity or operation. These can include:
➤
preventing 
fi res and explosions from spreading to 
other plant and equipment or to other parts of the 
workplace
➤
making sure that a minimum number of employees 
is exposed
➤
in the case of a process plant, providing plant and 
equipment that can safely contain or suppress an 
explosion, or vent it to a safe place.
In workplaces where explosive atmospheres may occur 
you should ensure that:
➤
areas where hazardous explosive atmospheres may 
occur are classifi ed into zones based on their likeli-
hood and persistence
➤
areas 
classifi ed into zones are protected from sources 
of ignition by selecting equipment and protective sys-
tem meeting the requirements of the Equipment and 
Protective Systems Intended for Use in Potentially 
Explosive Atmospheres Regulations 1996 although, 
equipment already in use before July 2003 can 
continue to be used indefi nitely provided to risk 
assessment shows it is safe to do so;
➤
where necessary, areas classifi ed into zones are 
marked with a specifi ed “EX” sign at their points 
of entry
➤
employees working in zoned areas must be pro-
vided with appropriate clothing that does not cre-
ate a risk of an electrostatic discharge igniting the 
explosive atmosphere
➤
before coming into operation for the fi rst time, areas 
where hazardous explosive atmosphere may be 
present are confi rmed as being safe (verifi ed) by a 
person (or organization) competent in the fi eld of 
explosion protection. The person carrying out the 
verifi cation must be competent to consider the par-
ticular risks at the workplace and the adequacy of 
control and other measures put in place.
13.9.6 Storage
Dangerous Substances should be kept in a safe place 
in a separate building or the open air. For fl ammable 
liquids that have a fl ashpoint above the maximum ambi-
ent temperature (normally taken as 32ºC), this small quan-
tity that may be stored in the workroom is considered to 
be an amount up to 250 litres.
For extremely and highly fl ammable liquids, and those 
fl ammable liquids with a fl ashpoint below the maximum 

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