Fire Safety on Construction Sites
Fire on a construction site can be catastrophic. Unlike completed buildings, construction sites often lack permanent fire detection systems, fire compartmentation may be incomplete, escape routes are constantly changing as work progresses, and large quantities of combustible materials are stored on site. The Regulatory Reform (Fire Safety) Order 2005 applies to all workplaces in England and Wales, including construction sites, and places a duty on the “responsible person” to carry out a fire risk assessment and implement appropriate fire safety measures.
Construction sites present unique fire risks because of the combination of hot works (welding, cutting, grinding), flammable materials (timber, solvents, LPG, adhesives), temporary electrical installations, and incomplete fire protection systems. According to the Fire Protection Association, there are approximately 600-800 fires on UK construction sites every year, with many causing significant damage, project delays, and occasionally injuries or fatalities.
The Fire Triangle
Understanding the fire triangle is fundamental to fire prevention. A fire requires three elements to start and sustain itself:
- Heat (ignition source) — sparks from grinding, welding flames, electrical faults, discarded cigarettes, sunlight through glass
- Fuel (combustible material) — timber, paper, cardboard, plastics, solvents, LPG, insulation materials, waste
- Oxygen (air) — present in the atmosphere at approximately 21%; some materials bring their own oxygen supply (oxidising agents)
Removing any one of these three elements will prevent a fire from starting or extinguish an existing fire. This principle underpins all fire prevention and firefighting strategies on construction sites.
Fire Extinguisher Types and Colour Codes
UK fire extinguishers are all red (to comply with BS EN 3) with a coloured band indicating the extinguishing agent. Every construction worker should know which extinguisher to use for each class of fire:
| Band Colour | Agent | Suitable For | NEVER Use On |
|---|---|---|---|
| Red | Water | Class A (wood, paper, textiles) | Electrical fires, flammable liquids, cooking oil |
| Cream | Foam (AFFF) | Class A and Class B (flammable liquids) | Electrical fires (unless tested), cooking oil |
| Black | CO₂ (carbon dioxide) | Electrical fires, Class B (flammable liquids) | Cooking oil (chip pan) fires |
| Blue | Dry powder | Class A, B, C (gases) and electrical | Not ideal in enclosed spaces (visibility), cooking oil |
| Yellow | Wet chemical | Class F (cooking oil and fat fires) | Electrical fires, flammable liquids |
The PASS technique describes the correct way to operate a fire extinguisher: Pull the pin, Aim at the base of the fire, Squeeze the handle, and Sweep from side to side. Only attempt to fight a fire if it is small, you have the correct extinguisher, you have a clear escape route behind you, and you are confident in doing so. If in any doubt, evacuate immediately.
Hot Works on Construction Sites
Hot works — any operation that involves open flames, produces heat, or generates sparks — is the single most common cause of fire on construction sites. Hot works includes welding, flame cutting, grinding, disc cutting, soldering, brazing, and using blowtorches. Strict controls are essential:
- A hot works permit must be issued for every hot works operation
- All combustible materials must be removed or protected within a minimum radius of 10 metres
- A suitable fire extinguisher must be immediately available at the work location
- A designated fire watch must be maintained during work and for a minimum of 60 minutes after completion
- The area must be checked for signs of fire or smouldering after the fire watch period
- LPG cylinders must be stored upright and away from ignition sources
Fire Classes
Fires are classified according to the type of fuel involved, which determines the appropriate extinguishing method:
- Class A — solid materials such as wood, paper, textiles, and plastics
- Class B — flammable liquids such as petrol, diesel, solvents, and paint
- Class C — flammable gases such as propane (LPG), butane, and natural gas
- Class D — combustible metals such as aluminium, magnesium, and titanium (rare on standard sites)
- Class F — cooking oils and fats (relevant to site canteens and kitchens)
- Electrical fires — not a formal class, but fires involving or caused by electrical equipment require specific extinguishers (CO₂ or dry powder)
Evacuation Procedures on Construction Sites
Every construction site must have a fire evacuation plan that is communicated to all workers during site induction. Key elements include:
- Fire alarm — a means of raising the alarm audible across the entire site (air horn, klaxon, or electronic system)
- Assembly point — a designated safe location away from the building and access routes for emergency vehicles
- Escape routes — clearly marked, kept clear of obstructions at all times, and regularly reviewed as the site layout changes
- Roll call — all personnel must be accounted for at the assembly point using the site register or signing-in system
- Fire wardens — trained individuals responsible for sweeping their designated areas and ensuring full evacuation
- Regular drills — practice evacuations should be conducted to ensure all workers know the procedure
Upon discovering a fire, the correct sequence of actions is: raise the alarm, evacuate the area, call the fire brigade (999), and only then attempt to fight the fire if it is safe to do so. Never re-enter a building once you have evacuated, and never use lifts during a fire evacuation.
Never use a water extinguisher (red band) on an electrical fire or a burning flammable liquid. Water conducts electricity and can spread burning liquids, making the fire significantly worse and putting you in immediate danger.