Our family has been experiencing a lot of colds and minor lung-associated problems, which seem to be increasing in frequency over the years. A friend suggested that our forced air heating system may cause it, but I’m not sure what that means or how it could be related to our illnesses. Do you see any possible connection(s) here?

There are only a couple of things that come to mind. Your friend may be referring to the potential for air borne contaminants to be spread through your home by the furnace duct system. The furnace fan is re-circulating house air (with some additional outside air) throughout the whole heating season. Apart from the obvious re-circulation of air borne bacteria there can be quantities of contaminants in the sheet metal ducts that carry the heat to each room and living area.

The main plenum ducts that carry the heat are large rectangular sheet metal boxes with lots of horizontal surfaces. Just like undusted shelves and ledges in any house, these flat surfaces load up with all sorts of air borne contaminants over time. Even along the troughs of the smaller round branch ducts heavy particles constantly settle out of the air and create dusty deposits in the troughs of the ducts. Germs and bacteria can easily transfer to the warm furnace air circulating over the duct surfaces so if you haven’t had your heat ducts cleaned recently this would be a good place to start.

As well, if your furnace is equipped with a built-in or after market humidifier consider disabling it by turning off the water supply, drying out the water tray and cleaning the unit thoroughly. Drum roller humidifiers can increase the opportunities for bacteria to spread through the house heating system because the water trays often collect and re-distribute bacteria through the heat ducts. Besides, most houses in the Kootenays do not need additional humidity. If a single room requires additional humidity consider installing a small portable humidifier and run it as little as required to satisfy the demand.    

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This article was written by Steven Cannon, a Registered Building Official and partner in Lynch Building Inspection Services Ltd. of Nelson, British Columbia. It originally appeared in The Nelson Express.

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