Flammable substances storage

Information on risk assessment for the safe storage of highly flammable substances in cabinets and separation from other dangerous substances

Highly flammable liquids are those that evaporate at room temperature. If the vapours are in the correct concentrations they will ignite in the presence of a flame or spark. The University needs to make sure that the storage is safe. This can be ensured by limiting the amount of liquid being stored and providing enough ventilation to prevent the concentration of flammable vapours reaching critical levels.

The Responsible Person must make sure a risk assessment has been undertaken to determine the quantity of highly flammable liquids that can be justifiably stored in any working area.

 

The objective is to ensure that in the event of an incident, people can safely escape from the laboratory. The risk assessment should therefore take into account: 

  • ignition sources in the work room and the potential fire spread in the event of ignition
  • the properties of the materials to be stored or handled in the working area
  • the amount of flammable liquids being handled that may be accidentally released or spilled
  • the means of escape from the laboratory or working area, e.g. limited single direction of escape or two directions of escape, unimpeded exit route/s, and travel distance to the outside of the room
  • the size of the laboratory or working area and the number of people working in it
  • exhaust ventilation provision in the laboratory or working area
  • the fire performance of the storage cabinet
  • the arrangements for closing the cabinet in the event of a fire
  • the maximum quantities that may be stored in cabinets are 50 litres for extremely, highly flammable and flammable liquids with a flashpoint below the maximum ambient temperature of the laboratory, and no more than 250 litres for other flammable liquids with a higher flashpoint of up to 55°C
  • for mixed storage all the materials being stored should be considered as being the same material as the one with the lowest flashpoint

When not in use, containers of flammable liquids will be kept closed and stored in suitable cabinets or bins of fire-resisting construction that are designed to retain spills (110% volume of the largest vessel normally stored in it).

 

The purpose of storing dangerous substances in cabinets is to provide a physical barrier to delay the involvement of these materials in a fire, for sufficient time for people's safety. 

Highly flammable cabinets should be constructed so:

  • that the materials used to form the sides, top, bottom and door(s) are capable of providing 30 minutes integrity in temperatures up to 400°C
  • that the joints between the sides, top and bottom of cupboards and bins should be bonded or fire stopped to prevent the passage of flames or hot gases
  • that the doors should be close fitting against the frame of the cabinet, so there is an overlap between the frame and doors in their closed position
  • that the supports and fastenings should be of a material with a melting point greater than 750°C
  • that the area designed to retain spills is large enough to take 110% of the largest vessel being stored
flamms cabinet drawing

Highly flammables cabinet with non-combustible walls with bonded or fire stopped edges, fire resisting doors and hinges. Bunded base capable of holding 110% of largest contained of 50 litres (55 litres)

 

These cabinets are not expected to protect the contents against the effects of a fire indefinitely. When the temperature is high enough to ignite the materials being stored (auto-ignition temperature) the fire will already be at flashover, so the contents should not make a significant contribution. 

Insulated cabinets are available which will protect the contents from the effect of fire by keeping the internal temperature under 200°C. These were originally designed to protect valuable materials such as archives, financial records and computer discs from fire.

The additional cost of insulated cabinets have to be weighed against the probability of a fire reaching flashover in the room and the potential contribution of the contents to the fire.

The flammable liquids must be stored separately from other dangerous substances that may enhance the risk of fire or compromise the integrity of the container or cabinet.

 

Other dangerous substances that may enhance the risk of fire or compromise the integrity of the container or cabinet/bin are, for example energetic substances, oxidizers and corrosive materials.

It's recognised that these other dangerous substances may be flammable liquids in their own right or held in a flammable liquid. However, it's still inappropriate to store these in the same cabinets or bins with other flammable liquids. 

All containers should have a legible label showing the contents so that mixed storage can be avoided.

The use of more than one storage cabinet within a room or laboratory will therefore be necessary to contain separated substances. It may also be necessary to provide more than one highly flammables cupboard in larger rooms or laboratories where it is not practical for users to share storage space. 

Fume cupboards are not designed or intended to be used as storage areas and they should be kept clear of materials and containers when these are not needed for the ongoing operational work. Materials stored in fume cupboards may disrupt the air-flow making the fume cupboard less efficient and compromising the safety of the user.  

Further guidance on Energetic and spontaneously combustible substances is contained in HS(G)131 published by HSE.