Fire hazards at work

Every workplace has fire hazards, but they differ greatly between an office, a restaurant, a warehouse, a factory, a laboratory, a hospital and a construction site. Recognizing the specific fuels, ignition sources and conditions that could combine to start a fire in your own workplace is the foundation of prevention. Fire hazard recognition is part of the wider hazard assessment process covered in HSE-103; this lesson applies that process to fire. It covers flammable and combustible liquids and gases, combustible dusts, electrical fire hazards, hot work, heating and cooking equipment, lithium-ion batteries, oxidizers and reactive chemicals, arson and waste, and how to look at a workplace through the eyes of a fire inspector.

Leading causes of workplace fires

Fire statistics vary by country and by type of property, but the same causes appear again and again in investigations of workplace fires: cooking equipment in restaurants and staff kitchens; electrical distribution and lighting equipment; heating equipment; hot work; intentional fires set by arsonists, often in waste and storage areas; smoking materials; and process equipment such as dryers, ovens and dust collectors. In industrial settings, flammable liquids, combustible dusts and process upsets add serious explosion risks. Knowing which causes are most likely in your sector focuses prevention where it matters most.

Flammable and combustible liquids

Flammable and combustible liquids are among the most common serious fire hazards at work: fuels, solvents, paints, thinners, adhesives, cleaning products, alcohols and many process chemicals. Under the Globally Harmonized System used in WHMIS and HazCom (HSE-102), flammable liquids are classified into categories by flash point and boiling point, with Category 1 being the most hazardous. Fire codes also use older terms: flammable liquids, with flash points below about 37.8 °C (100 °F), and combustible liquids, with higher flash points. The main hazards are vapors that travel along floors to distant ignition sources, because most flammable vapors are heavier than air; spills that spread fire rapidly; containers that rupture when heated; and static electricity generated when liquids are transferred. Basic precautions include using the smallest practical quantity, keeping containers closed, storing liquids in approved safety cans and flammable storage cabinets, bonding and grounding containers when transferring liquids, ventilating work areas, and keeping ignition sources away. Lesson 3 covers storage in more detail.

Flammable gases and compressed gas cylinders

Flammable gases such as propane, natural gas, acetylene and hydrogen ignite easily and can form explosive mixtures in enclosed spaces. Leaks may be invisible and, for odorless gases, undetectable without instruments. Compressed gas cylinders also store large amounts of energy: a cylinder heated in a fire can rupture violently, and a cylinder whose valve is broken off can become a projectile. Cylinders must be secured upright, capped when not in use, stored away from heat and from incompatible gases (for example, oxygen cylinders separated from fuel gases), and checked for leaks with approved methods. Oxygen deserves special mention: oxygen itself does not burn, but an oxygen-enriched atmosphere makes ordinary materials such as clothing ignite easily and burn fiercely. Oxygen must never be used to blow dust off clothing or to "freshen" the air in a confined space.

Combustible dust

Many solid materials that are hard to ignite in bulk become explosive when they are ground into fine dust and dispersed in the air: wood, flour, sugar, grain, starch, plastics, pharmaceuticals, coal, and metals such as aluminum and magnesium. A dust explosion requires five conditions, sometimes called the dust explosion pentagon: fuel (the dust), oxygen, an ignition source, dispersion of the dust in air, and confinement. A small primary explosion, for example inside a dust collector, can shake loose dust that has accumulated on beams, ledges and ducts, creating a much larger secondary explosion that tears through a building. Major disasters, such as the 2008 sugar refinery explosion at Port Wentworth, Georgia, which killed 14 workers, and the 2012 sawmill explosions in British Columbia at Burns Lake and Prince George, which killed four workers in total, have shown how devastating dust explosions can be.

Controls for combustible dust include capturing dust at the source with properly designed dust collection; regular housekeeping that removes accumulations from all surfaces, including high and hidden ones, using methods that do not create clouds (such as approved vacuums rather than compressed air); controlling ignition sources, including static electricity and hot surfaces; and engineering protection such as explosion venting, isolation and suppression. Where combustible dust is present, a dust hazard analysis by a qualified person is the starting point, and specialized standards apply.

Electrical fire hazards

Electrical faults are a leading cause of fires in all kinds of buildings. Common hazards include overloaded circuits and power bars, especially when power bars are plugged into one another ("daisy-chained"); extension cords used as permanent wiring, run under carpets or through doorways where they are damaged; damaged cords and plugs; loose connections that overheat; equipment placed against combustibles or with blocked ventilation; and missing covers on electrical boxes and panels. Electrical rooms used as storage add fuel next to ignition sources, and blocked access to electrical panels delays shutting off power in an emergency. Simple controls go a long way: inspect cords and plugs before use, use equipment certified for the purpose, unplug appliances that are not in use, keep clearance in front of electrical panels, report warm outlets, flickering lights or burning smells, and leave electrical repairs to qualified electricians. HSE-213 and HSE-214 cover electrical safety in depth.

Lithium-ion batteries

Lithium-ion batteries power laptops, phones, tools, forklifts, scooters, e-bikes, energy storage systems and electric vehicles. When a cell is damaged, overcharged, manufactured with defects, exposed to heat or short-circuited, it can enter thermal runaway: an uncontrollable chain of heating that vents flammable and toxic gases and can spread from cell to cell. Battery fires burn intensely, can re-ignite hours or days later, and may produce explosive gas mixtures in enclosed spaces. Workplace precautions include buying certified batteries and chargers, using only the charger supplied for the device, charging in designated areas away from combustibles and exits, not charging unattended overnight where avoidable, inspecting for swelling, damage or heat, removing damaged batteries from service and storing them safely, and following site rules for e-bikes and scooters, which many workplaces now restrict indoors. Large battery energy storage systems require specialized fire protection and emergency planning.

Heating, cooking and process equipment

Portable space heaters are a frequent cause of fires when placed too close to paper, curtains or clothing, left running unattended, or knocked over. Many workplaces restrict their use or require models with tip-over and overheat protection and a minimum clearance, often about one meter, from combustibles. In commercial kitchens, grease accumulates in exhaust hoods, filters and ducts and can carry a fire from a fryer into the building structure; regular cleaning and inspected kitchen fire suppression systems (Lesson 5) are essential. Industrial ovens, dryers, furnaces and kilns need maintained safety controls, and process equipment such as hydraulic systems can spray oil mist onto hot surfaces if a hose fails. Maintenance programs that inspect and clean such equipment are part of fire prevention.

Hot work

Welding, cutting, brazing, soldering, grinding and torch-applied roofing cause many serious fires, often after the work has finished and workers have left. Sparks and slag can travel more than 10 m horizontally, fall through gaps in floors and walls, and smolder in hidden places for an hour or more before flaming. For this reason, hot work outside designated welding areas is controlled by a hot work permit system, which requires clearing or protecting combustibles within a defined radius, having extinguishers and a trained fire watch present during the work and for a period afterward, and inspecting the area before leaving. HSE-212 covers hot work and permits in depth.

Oxidizers, reactive chemicals and self-heating materials

Oxidizing chemicals, such as nitrates, chlorates, perchlorates, permanganates, peroxides and concentrated nitric acid, supply oxygen to fires and can cause organic materials to ignite on contact. Some chemicals react violently with water, air or each other, and some materials heat themselves: oily or solvent-soaked rags, linseed oil, certain metal powders and large piles of damp organic materials can heat spontaneously until they ignite. Segregating incompatible chemicals, following the storage and incompatibility information on safety data sheets, and disposing of oily rags in approved self-closing metal containers emptied daily are simple, effective controls.

Arson, waste and housekeeping

Deliberately set fires are a significant cause of fire damage to businesses, and they usually start where fuel is easy to reach: waste bins and dumpsters against buildings, pallets and packaging stored outside, and unlocked storage areas. Keeping waste containers away from walls and openings, keeping outdoor storage tidy and secured, controlling access, lighting the perimeter and investigating small fires promptly reduce the risk. Inside, accumulations of paper, cardboard and packaging give small fires the fuel to grow. Good housekeeping, discussed in Lesson 3, is one of the most effective fire prevention measures.

Looking at a workplace through an inspector's eyes

A fire hazard walk-through applies the fire tetrahedron systematically: where are the fuels, where are the ignition sources, and where could they meet? A structured approach looks at each area in turn and asks about storage of flammables and combustibles, condition of electrical equipment, heating and cooking appliances, hot work, waste and housekeeping, means of escape and fire doors, fire protection equipment and its access, and unusual hazards such as dust, batteries or oxygen. Findings are recorded, rated using the risk methods in HSE-103, and assigned for correction.