This silent killer claims about 1,500 lives each year in the U.S.

Carbon monoxide (CO) is one of the toxins that remains from incomplete combustion of fossil fuels. Fossil fuels include oil, gas, and coal. Small amounts of CO, such as those emitted from the kitchen range, will usually be found in the air in the home. These amounts will pose no health concerns for the occupants.

However, health problems can develop if one is exposed to CO in large amounts, such as those emitted for many hours from a blocked chimney. In extreme cases, the presence of CO can be lethal. 

There has been a lot written about heating systems causing dangerous levels of  CO gas in homes. The heating furnace itself will not cause CO gases of any concern to be emitted into the home.

If the heat exchanger fails (the heat exchanger is the part of the furnace that keeps burned fuels separate from the air in the living space), it is rare that CO is emitted in the air. If CO is emitted; the amount re­leased is not significant. Here’s the reason why:

The typical furnace has a fan that circulates the indoor house air to and from the heating system and living space. This fan creates approximately 18 times more pressure on the house side air than the typical pressure created by atmospheric burners. In the presence of a failure, this pressure causes the air from the living space to pass to the exhaust side of the unit and up the chimney.

This is not to say that a failed heat exchanger is acceptable. It is not. However, the likelihood of significant CO gas being delivered to the living space has been grossly overstated. The single item that would deliver dangerous amounts of CO gas to a dwelling is a chimney that is blocked for many hours or days.

Carbon monoxide in homes is difficult to research due to numerous variables, including:

1)   The size and air volume of a home: The more air in the home, the easier gases will dissipate.

2)   The number of air changes in a home: Older homes are likely to have considerably more air changes per hour than modern homes that have thick insulation, etc.

3)   The type of construction: Various types of frame and masonry construction will have an effect on air changes and air infiltration.

4)   The type of heating system: Combustion air requirements and efficiences have some effect on air movement and changes.

5)   Operating fans and exhaust systems: When on, these systems dissipate all the air in the house in minutes. The size of the systems and the house will determine how effectively this is done. 

According to an American National Standards study on heat exchangers, leakage of waste gases is acceptable as long as the combustion chamber and vent do not leak more than 2% of flue gases. (Testing parameters are. 1” water column static pressure on the interior of tile heat exchanger)

CO poisoning kills about 1,500 people a year. CO reduces the ability of the hemoglobin in the blood to carry oxygen to the brain and body. This is akin to not breathing. The blood recovers quickly if the exposure is not continuous. Typical symptoms include headaches, fatigue, insomnia, nausea, and heart palpitations.

The presence of CO in a home can cause physiological effects at any level. However, the following parts per million (ppm) indicate when it is a serious concern:

     50 ppm Allowable for up to 8 hours of exposure

    500 ppm Can be inhaled for one hour without appreciable effect

    700 ppm Some effects after one hour of exposure

1,200 ppm Unpleasant, but not dangerous, effects after one hour of exposure

2,000 ppm Dangerous effects after one hour of exposure

4,000 ppm Fatal in less than one hour

The most desirable condition would be a zero level of CO. To achieve low and safe levels, use a CO monitor. It will detect when levels surpass 10 ppm.

As of March 6, 2003 every one and two family home, co-op or condo constructed or offered for sale requires a functioning carbon monoxide detector.

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