Fire Prevention & Extinguishers

Most site fires don't start with a bang. A spark from grinding or cutting lands in something combustible and smolders unnoticed until everyone's moved on. The two questions worth asking today are whether we'd stop that happening, and whether we'd know what to do if it did.

The hazard

A construction site is stacked with fuel: framing lumber, packaging, foam, form oil, fuels, solvents, fine dust. Hot work — welding, cutting, grinding, torching — throws sparks and heat that can smolder for hours before it flares. As the weather cools, temporary heaters and fuel storage add to it. Ontario requires firefighting equipment at readily accessible, clearly marked locations, and workers who may have to use it to be trained on it. Meeting that on paper isn't enough on its own — a small fire doubles fast, and it can cut off the only way out.

What to do

• Work to the hot-work permit. Pull one before welding, cutting, or grinding. The permit — not a remembered number — is what sets the clearance distance, the shielding, and how long the fire watch runs afterwards, because those figures come from the applicable fire code and your site's own procedure rather than from the construction regulation.
• Clear the fuel or shield it. Move combustibles well back from the work, or cover them properly. Sparks fall, roll, and drop through gaps you can't see — check the level below and inside wall cavities before you strike an arc.
• Post the fire watch, and keep it going after the work stops. The watch is someone whose only job is looking for fire, during the hot work and for the period the permit specifies afterwards. Most hot-work fires start after the welder has packed up — the "after" is the part crews skip.
• Know the extinguisher rating. Every fire extinguisher on an Ontario project has to be a pressurized type rated at least 4A40BC. A 2A:10B:C unit doesn't meet it. Keep them charged, tagged, protected from damage and freezing, and where you can actually reach one without walking into the fire or losing your way out.
• Know PASS, and know the limit: Pull the pin, Aim at the base of the flames, Squeeze, Sweep. An extinguisher is for a small fire you're confident about, with your exit behind you. Anything bigger, or any doubt: get everyone out, call it in, close the door if you can.
• Protect the exits. Stairs, ramps, and travel routes stay clear, and nothing parks in front of an extinguisher.
• Store fuels properly — approved containers, away from heat, sparks, and ignition sources, per the applicable code and your site's storage arrangement.

Watch out for

• Sparks dropping to a lower floor or into a wall cavity where nobody's watching them.
• An extinguisher with a low gauge, a broken seal, or a missing tag — a dead extinguisher is worse than none, because you'll trust it.
• The wrong rating quietly in place because somebody bought what was on the shelf.
• Reaching for an extinguisher on a fire that's already bigger than a bucket.

Talk it over

• Where's the nearest extinguisher to our work right now, what's its rating, is it charged, and who here has actually used one?
• For today's hot work: what does the permit say about clearance and how long the watch runs after we stop?
• If a fire started between us and the stairs, what's our second way out?