Storing Flammable Substances Indoors
The Dangerous Substances and Explosive Atmospheres Regulations 2002 require risks from indoor storage to be controlled by elimination or by reducing the quantities of substances to a minimum and by providing mitigation to protect against foreseeable incidents.
The HSE highlights that it is the responsibility of the employer/duty holder to justify the need to store any particular quantity of flammable liquid but the guiding principle is that “only the minimum quantity needed for frequently occurring activities or that required for use during ½ day or one shift should be present”.
The HSE also states that the maximum quantities that may be stored in cabinets and bins are no more than 50 litres for extremely flammable and highly flammable substances, and those flammable liquids with a flashpoint below the maximum ambient temperature of the workroom/working area and no more than 250 litres for other flammable liquids with a higher flashpoint of up to 55°C.
When not in use, flammable solvents must be stored in suitable “cabinets or bins of fire-resisting construction and which are designed to retain spills (110% volume of the largest vessel normally stored in it)”. These should be located in designated areas, where possible away from the immediate processing area and not impeding means of escape.
The HSE Approved Code of Practice for DSEAR (L138) details the performance requirements for fire-resisting cupboards and bins as follows:
- Every side, top, floor, door and lid should provide a minimum of 30-minutes’ fire resistance in respect of integrity
- If there is need for a viewing panel on an oven used for the evaporation of dangerous substances, this should be provided by using Georgian-wired glass or a proprietary fire-resisting glazing panel.
In all other circumstances, the fire resistance integrity requirements should be maintained for cabinets, enclosures, cupboards and bins which should:
- be constructed of materials which are, so far as reasonably practicable, of ‘minimal risk’ in respect of their reaction to fire;
- be supported and fastened to prevent structural collapse in case of fire for at least 30 minutes. The supports and fastenings should be of high melting point material (in excess of 750 °C Cabinets, ovens, cupboards, bins, ducts, trunks and casings should be bonded or fire-stopped to prevent or retard the passage of flame and hot gases for a period of at least 30 minute
Many organisations will use cabinets built to BS EN 14470-1:2004 Fire Safety Storage Cabinets. Safety Storage Cabinets for Flammable Liquids, which may go beyond the minimum requirements of UK health and safety legislation.
The HSE notes that it is the responsibility of the employer/duty holder to ensure that cabinets to any particular standard or design specification meet the minimum legal requirements, but give a cautionary message in that “the use of cabinets with enhanced fire performance should not be seen as a substitute for the provision of dedicated store rooms and outdoor storage areas for the safe keeping of containers which are nominally empty or are not needed for current work”.
Procedures for dealing with emergencies related to the hazardous substances being stored need to be developed. Consideration needs to be given to the range of possible events, including:
- Releases, e.g. leakages or spillages.
The following factors must also be taken into account when storing flammable substances.
- The nature and quantities of the dangerous substances stored.
- The location and design of the storage facility.
- The people, both on and off the site, who may be affected.
Safe systems of work for dealing with spillages and leakages should be put in place and will depend on the nature of the substance involved.