Carbon Monoxide & Smoke Detectors

Smoke Detectors - It's The Law

Effective March 1, 2006, it became law for all Ontario homes to have a working SMOKE ALARM on every storey and outside all sleeping areas.

With this previously announced Fire Code amendment now in effect, it is hoped there will be a reduction of the number of preventable fire-related injuries and fatalities.  The amendment covers single family, semi-detached and town homes, whether owner-occupied or rented.


Penalties for non-compliance with the Ontario Fire Code smoke alarm requirements could result in a ticket for $235 or a fine of up to $50,000 for individuals or $100,000 for corporations.

 Carbon monoxide detectors are now MANDITORY in every home.

What is carbon monoxide?

Carbon Monoxide (CO) is a colourless, odourless, tasteless and toxic gas which is flammable/explosive within certain concentrations in air. When inhaled it inhibits the blood's capacity to transport oxygen throughout the body. It can poison the body quickly in high concentrations, or slowly over long periods of time in lower concentrations.



What are the symptoms of carbon monoxide poisoning?

Exposure to CO can cause flu-like symptoms such as headaches, nausea, dizziness, burning eyes, confusion, drowsiness or loss of consciousness. In severe cases, CO poisoning can cause brain damage and death. The elderly, children and people with heart or respiratory conditions may be particularly sensitive to CO.

How is carbon monoxide generated in the home?

Carbon Monoxide is a byproduct of incomplete combustion of fuels such as natural gas, propane, heating oil, kerosene, coal, charcoal, gasoline or wood. This incomplete combustion can occur in any device that depends on burning for energy or heat, such as furnaces, room heaters, fireplaces, hot water heaters, natural gas or propane stoves or grills and any gas-powered vehicle or engine.

Automobiles left running in attached garages, gas barbeques operated inside a house or garage, grills or kerosene heaters that are not properly vented or chimneys or vents that are dirty or plugged may create unsafe levels of CO. When properly installed, maintained and vented, any CO produced by these devices will not stay inside the home.

What are some danger signs?

  •     You or other members of your family have symptoms of exposure (see above).
  •     You notice a sharp, penetrating odour or smell of gas when your furnace or other fuel burning equipment turns on.
  •     The air is stale or stuffy.
  •     The pilot light of your furnace or other fuel-burning appliance goes out.
  •     Chalky white powder forms on the chimney/exhaust vent pipe or soot build-up occurs around the exhaust vent.

How can unsafe levels of CO be detected?

CO alarms monitor airborne concentration levels (parts per million) of CO and sound an audible alarm when harmful CO levels are present. Be sure that your alarm has been certified to the Canadian Standards Association CAN/CGA 6.19 standard or the Underwriters Laboratories (UL) 2034 standard.

What to do if you suspect CO in your home.

  1.     Leave the home immediately.
  2.     Leave the door open.
  3.     Call 911 from a neighbour's phone. Tell them the details and whether you are suffering symptoms of CO poisoning (see above).
  4.     When a CO detector alarms, do not assume it to be a false alarm.
  5.     If there is a strong smell of natural gas in your home, evacuate immediately. Call 911 from a neighbour's home and contact the gas company that services your home.
  6.     If, after the fire department checks out the home symptoms re-occur or persist, exit the home, contact your gas company and provide them with the details. Do not re-enter the home until a qualified utility or heating contractor checks all fuel-burning appliances.

Where should a CO detector be located in the home?

Proper placement of a CO alarm is important. In general, the human body is most vulnerable to the effects of CO during sleeping hours, so an alarm should be located in or as near as possible to the sleeping area(s) of the home. If only one alarm is installed, it should be located near the sleeping area, where it can wake you if you are asleep. Where sleeping areas are located in separate parts of the home, an alarm should be provided for each area.

Additional CO alarms should be placed on each level of a residence and in other rooms where combustion devices are located (fireplace, gas clothes dryer or natural gas furnace, for example), or adjacent to potential sources of CO (such as a teenager's room or granny suite located adjacent to an attached garage).

Unlike smoke, which rises to the ceiling, CO mixes with air. Recognizing this, a CO alarm should be located at knee-height (which is about the same as prone sleeping height on a bed). Due to the possibility of tampering or damage by pets, children, vacuum cleaners and the like, it may be located at chest height. To work properly, a CO alarm should not be blocked by furniture, draperies or other obstructions to normal air flow.

If a combination smoke/carbon monoxide detector alarm is used, it should be located on the ceiling to ensure that it will detect smoke effectively. Always refer to the manufacturer's instructions for additional information regarding proper installation, use and maintenance.

Carbon Monoxide Detectors: Is one really necessary?

Unanticipated dangerous incidents may occur despite your best efforts to avoid CO. The installation of at least one CO detector in your home is a good safety precaution. A detector might be your second line of defence, but it is necessary. You should have one in your home today.

There are performance differences between these detector types. However, changes to the CO standards have resulted in all detectors, regardless of detector type, having to undergo extensive testing. All are certified to operate under different environments (various chemical exposures, different relative humidities, etc.) satisfactorily if they meet the standards.

How does a CO detector work?

There are three basic types of CO sensors — metal oxide, biomimetic and electrochemical. Each is discussed in the chart below. Note that while there may be performance differences between these technologies, all detectors are tested and approved for their operation.The retail cost of a detector will generally relate to the number of features included and its warranty conditions.

  Metal Oxide Semi-conductor (MOS) Biomimetic   Electrochemical
How does it work? The original technology for detecting CO. Heated tin oxide reacts with CO to determine the levels of the toxic gas. Must connect to house power. Gel-coated discs darken in the presence of CO. Colour change sounds an alarm. Chemical reaction with CO creates an electrical current, setting off an alarm.
Features No need to remember to check batteries as the unit plugs in.

Battery backup is available for up to 20 hours.

- Less expensive technology.
- Can be battery operated.
- Highly sensitive and accurate readings at all CO levels.
- Most units come with a continuous digital readout and a memory feature that allows you to check past CO levels.
- Fast reset time.
- Most units sound an alert when sensor needs replacing.


Carbon Monoxide Detectors and Charging of Lead Acid Batteries

When charging lead acid batteries, hydrogen (H2) gas is produced. Hydrogen gas is a by-product from the electrolysis reaction (charging) of the lead acid battery. Hydrogen gas can interfere with the carbon monoxide detector's sensor. The carbon monoxide sensor is sensitive to and will respond to hydrogen gas at about a 10 to 15 % of it's actual concentration. If you find you are getting high carbon monoxide readings around battery charging operations do not be alarmed, but be cautious. The Lower Explosive Limit (LEL) for hydrogen is 4.0 % by volume (40,000 ppm by volume). If your carbon monoxide detector alerts, and you are charging a lead acid battery in the area, disconnect the battery charger and ventilate the space in order to dissipate the gas.

The public should be aware of the limitations and interferences that can affect CO detectors. CO detectors are electrochemical sensors, which detect a variety of specific gases. In most cases, the gas of interest reacts with the chemical solution in the sensing electrode to produce ions (charged particles) that move through the solution to an electron-accepting electrode, completing an electric circuit. The number of ions produced and the magnitude of the current developed are proportional to the concentration of the gas being measured.

Additional interfering gases of similar molecular size and chemical reactivity may produce false positive response. Major interferents that can affect CO detectors are acetylene, dimethyl sulfide, ethyl alcohol, ethylene, hydrogen cyanide, hydrogen sulfide, isopropyl alcohol, mercaptan, methyl alcohol, propane, nitrogen dioxide, and sulphur dioxide.

Fire Engineering, September, 1996.