Carbon Monoxide Detectors - Important Information You Should Know

November 21st 2003
Carbon Monoxide Detectors - Important Information You Should Know

Due to some recent concerns regarding Carbon Monoxide poisoning, ULC has provided the following information on Carbon Monoxide Detectors to consumers:

Carbon Monoxide (CO) detecting devices are designed to detect levels of CO below critical levels.

When CO levels reach a specified value (measured in parts per million, ppm), an 85 dB alarm will go off (the same level of loudness as a smoke alarm).

Some units have displays that give relative levels of CO either by numeric value or by a series of warning lights or audible chirps.

Three types of methods and/or technology are used to detect CO:

Biomimetic (mimics body response) - usually battery operated, but sensitive to temperature and humidity, the sensor lasts approximately 6 years. This technology uses gel-coated discs that darken in the presence of CO, tripping the alarm.

Oxide Semi-conductor (most common) - usually plugged into wall, uses Metal Oxide sensor that requires more power, it is sensitive to moisture and lasts approximately 5-7 years. With this type of technology, heated tin dioxide reacts with carbon monoxide to determine levels of toxic gas.

Electrochemical (least common, more accurate) - expensive, battery operated, short sensor life. With this type of sensor, three platinum electrodes in an electrolyte solution generate energy when they react with CO.

Within Canada, there are leading manufacturers of CO Gas Alarms. ULC investigates, tests and certifies CO gas alarms to the National Canadian Standard.

ULC certifies products from a number of manufacturers including:

- American Sensors Electronics Inc.;

- Atwood Mobile Product;

- BRK Brands Inc. (First Alert);

- Coleman Safety and Security Products Inc.;

- Jameson Home Products Inc.;

- Maple Chase Company;

- North American Detectors Inc. (American Sensors, CO-Smoke Response);

- Patric Plastics Inc. (S-Tech);

- Safety Developments International Canada Ltd. (Guardian).

The use of CO Alarms is encouraged in recreational vehicles as well as permanent residences.

Look for the ULC mark to be sure the product has been tested and certified by ULC.

Common Sources of Carbon Monoxide

Leaky heat exchangers in furnaces.

Improper or blocked exhaust vents for gas appliances.

Wood burning appliances e.g. fireplaces or stoves that may be blocked or improperly vented.

Idling vehicles in garages attached to houses.

Underground garages.

Large collections of idling vehicles.

Facts about CO



Same weight as air

Disperses rapidly in air

Can percolate through concrete for hours after vehicles have left the garage

Gas forms when fuels like natural gas, oil or wood do not burn completely in appliances such as furnaces and stoves, water heaters, ranges and ovens.

Symptoms of CO Poisoning

Exposure to low levels of CO can cause nausea, vomiting, dizziness, headaches, confusion, fatigue

High level exposure can cause abdominal pain, diarrhea, impaired vision, convulsions, coma and eventually death

Everyone should have at least one CO gas alarm near their sleeping areas. Read and keep instructions to determine what you should do if alarm sounds.


Each UL listed carbon monoxide detector bears a label which reads:

UNDERWRITERS' LABORATORIES OF CANADA LISTED CARBON MONOXIDE DETECTOR together with the listee's name, model designation and electrical rating.

Install one or more carbon monoxide alarms that are certified to the latest Canadian Standards Association (CSA) standards. Products with CSA 6.19-01 on the packaging have been tested to the latest standard published in March 2001. The package will also show a replacement date.