Carbon Monoxide Alarm — Emergency Guide

Carbon monoxide (CO) is a colourless, odourless and toxic gas produced by incomplete combustion. In a commercial or institutional building, a CO alarm is not an equipment fault to be diagnosed on the spot: it is a life-safety event. This guide covers the B2B response — it does not replace your facility’s emergency protocol or the instructions of emergency services.

What should you do the moment a CO detector goes off?

Follow your building’s evacuation protocol. The accepted principles: get occupants out of the affected area, do not go back in to “check” the appliance, and call 911 from outside. Anyone with headaches, nausea, confusion or drowsiness needs medical attention — the symptoms of CO poisoning resemble the flu and can worsen without warning. If your procedure calls for shutting down a combustion appliance and the control is reachable without entering the affected area, it can be operated; otherwise, leave it to the responders. Once the site is secured, bring in a qualified team — our emergency repair service — before anything is restarted.

Where does carbon monoxide in a mechanical room come from?

Carbon monoxide appears when combustion is starved of air or when flue gases are not properly evacuated. The usual leads overlap: a blocked, corroded or badly connected vent, insufficient combustion air (obstructed air intake, a room depressurized by exhaust fans), a misadjusted or fouled burner, a cracked heat exchanger letting flue gases through, or spillage tied to draft. A blocked vent or air intake is a classic during freeze and snow conditions. An appliance can look like it is running normally while producing CO: only measurement reveals it.

What benchmarks apply, and how is service restored?

In Québec, the Regulation respecting occupational health and safety sets permissible exposure values for carbon monoxide in the workplace: 35 ppm as an 8-hour time-weighted average and 175 ppm as a short-term exposure value. These are occupational hygiene benchmarks for the employer — not alarm trip points, and not a licence to occupy a space that is in alarm. Service is restored after the source is identified and corrected, venting and combustion air are verified, and an instrumented combustion analysis is performed. Montréal Combustion serves Greater Montréal, the North Shore and the South Shore: structured diagnostics, return to compliance and safe restart of gas-fired installations. 450-473-0909.

Frequently Asked Questions

Could a CO alarm be a false alarm?

A detector can be past its service life or poorly located, but that is never assumed on site. Treat every alarm as real: get occupants out, call emergency services and let an instrumented measurement settle it. Carbon monoxide is odourless and colourless, so the absence of a smell proves nothing.

Does a carbon monoxide detector also pick up a natural gas leak?

No. A CO detector measures a product of incomplete combustion, while a combustible gas detector responds to unburned methane. These are two distinct devices covering two different risks, and a mechanical room may need both depending on the installation.

Can the appliance be restarted after a CO alarm?

Not until a qualified technician has identified the source and corrected the cause. Return to service requires verifying flue gas evacuation and combustion air, plus a combustion analysis on the appliance involved.