The Risk of Fire & Explosion
(Acknowledgement – Andrew Lawrence of Empteezy)
Flammable substances such as solvents and fuels are present in many workplaces, but they can cause devastating fires and explosions if handled incorrectly. This can be avoided by properly assessing the risks and adopting precautions such as safe storage.
The risk of fire and explosion from substances such as chemicals, solvents, fuels and fuel gases is ever present in many working environments. The problem occurs because as well as being highly flammable, if many of these substances are exposed to the air they evaporate, causing dangerous vapours to accumulate. This in turn poses a serious risk of ignition or explosion.
It goes without saying that this scenario can lead to major loss of life and serious injury, as well as significant damage to property. As a result, employers working with and handling dangerous substances such as chemicals, fuels and gases have a legal obligation to tackle the associated fire
and explosion risks. This means preventing the release of dangerous substances; preventing or controlling sources of ignition; ensuring that products are stored correctly; and establishing appropriate procedures for the delivery, handling and use of these substances.
Employers should firstly attempt to completely eliminate the fire and explosion risks from dangerous substances – for example, by using a non-hazardous substance. But if this proves impractical, measures must be taken to control the risks and mitigate the effects of any fire or explosion. Control measures must be applied in a priority order, starting with reducing the quantity of the dangerous substance to a minimum. Mitigation measures will include reducing the number of employees exposed to the hazard and providing staff with suitable personal protective equipment.
One area that employers should pay close attention to when preventing fires and explosions is the safe storage of flammable liquids in process areas, workrooms, laboratories and similar working areas. Regulations (and best practice) apply to the indoor storage of all flammable substances – employers must eliminate or control the risk, reduce the quantity of substances stored on site and mitigate the effect of any foreseeable fire or explosion. Three elements must be present for a fire to start; heat, oxygen and fuel, and if one of these can be removed, the risk of a fire will also be removed. Heat can be any ignition source which generates heat, such as a mechanical spark, static electricity, or a naked flame from welding equipment. Oxygen is of course present in the air, while fuel can be any flammable or combustible liquid or vapour. Some of the general principles to follow when storing or working with flammable or explosive substances at work are explained below.
Flammable liquids must be stored in a separate area of the workplace in purpose made bins or cupboards that comply with South African regulations. During dispensing, there must be good ventilation and sources of ignition – such as a spark from a tool or electrical component – must be removed. Containers should also be kept closed when not in use, and whenever possible safety containers with self-closing lids and flame arresters should be used. It is also a good idea to have a suitable spill kit on hand to capture any leaks which could pose a safety or pollution risk.
If flammable or explosive dusts are present steps must be taken to remove any sources of ignition – for example, by ensuring that no naked flames are present. Work areas should also be regularly cleaned to keep them dust-free.
Many types of packaging material such as plastic foam, polyester wadding and textiles give off dense black smoke when they burn, so they should not be stored close to heaters or electrical equipment which could act as an ignition source.
Gases are often stored at very high pressure and any uncontrolled release can fill a large area quickly. This is particularly the case with liquefied gases such as LPG. As a result, gas cylinders should be stored in a designated area in purpose built stores. The cylinders should also be restrained and you should try to protect the valves from potential damage caused by impacts.
Materials that ordinarily burn slowly, will burn vigorously in an oxygen rich atmosphere, so oxygen cylinders must also be stored in a secure and controlled manner. In addition, oxygen must never be used as a substitute for compressed air, or to sweeten the air in a working area or confined space. Furthermore, grease or oil must not be used on equipment containing oxygen as they can self-ignite.
Some chemical products incorporating organic peroxides can explode if not stored and handled correctly and certain chemical substances can react with incompatible materials or contaminants, causing an explosion. For example, oxidising chemicals can cause flammable materials to ignite and some substances such as sodium react violently when they come into contact with water. In addition, chemical products should be stored and used at the recommended temperatures to prevent dangerous decomposition or unwanted reactions. Information on storage and handling temperatures can be found in the substance’s material safety data sheet (MSDS)or by contacting the manufacturer.
Using flammable liquids
If flammable liquids are used in a work process, it is likely that a limited quantity will have to be stored and readily available inside the workplace. In assessing the risks from flammable substances, employers will need to justify the requirement to store any particular quantity of flammable liquid within the work room or working area. However, the guiding principle is that only the minimum quantity needed for frequently occurring activities or an amount required for use during half a day or one shift should be present in the work room. The actual quantities allowed inside the work area or building will depend on the work activity and also the arrangements in place for controlling the fire risks. When not in use, containers used for storing flammable liquids needed for ongoing work should be kept closed and placed in suitable fire-resistant cabinets or bins which are also designed to retain spills. The cabinets should be located in designated areas that do not interfere with any escape route from the working area. Ideally, this will be away from the processing area. Flammable liquids should also be stored separately from other dangerous substances that pose a risk of fire or which could compromise the integrity of the container. For example, substances with oxidising and corrosive properties should not be stored together.
Maximum storage quantities
The local Fire by-laws dictate the maximum quantities of flammable substances that should be stored within your premises without a flammable substance certificate. It is recommended that you liaise with your local fire department for the maximum allowable quantities applicable to your area. Typically, these limits are no more than 40 litres of class I (flash point of < 37 deg C) and 200 litres of class II and III liquids (flash point > 37 deg C) .
If dangerous substances such as oils and chemicals are stored externally, employers also need to ensure they do not pose a risk of polluting nearby drains or watercourses. Companies can be prosecuted for such incidents even if the problem is caused by vandals. Employers must therefore think about the amounts of products that need to be stored; the types of containers they are held in (for example, 205 litre drums or 1,000 litre intermediate bulk containers); and the need for spill pallets or standalone stores with built-in sumps to capture spills and leaks. The bund of any storage unit or a spill pallet must be able to contain at least 110% of the volume of the largest container or 25% of the total volume stored, whichever is greater. They must also be made of a material compatible with the chemical being stored. Storage areas should also be located in suitable areas, for example, away from drains and staff should also be trained on how to deal with spills. Spill kits and absorbent materials should be present on site and a pollution incident response procedure should be drawn up and followed at all times. It is always better to try to keep any spill of hazardous substances on the surface, so spill kits should be located next to chemical and oil storage areas and sealing products should be positioned next to the site drains. An inventory of all the chemicals on site should be drawn up and should be kept in a location where it can be easily accessed by spill responders or outside agencies, such as the fire service. The location of spill containment equipment should also be marked on a site plan, and this too should be readily available to staff or emergency responders.