Safe Home

Caring for Your Chimneys & Flues

When gas and oil burn in vented heating systems – in order to produce household heat – the dangerous fumes that are by-products of combustion range from soot (particulate matter) to nitrogen dioxide (also toxic) to acidic water vapors formed when moisture condenses. None of these pollutants should be allowed to leak from the chimney into your living space.

In addition to carrying off toxic gases, chimneys also create the draft (flow of air) that provides the proper air and fuel mixture for efficient operation of the heating appliance – whether a furnace or boiler. Unfortunately, many chimneys in daily use in homes throughout the country either are improperly sized or have conditions that make them unable to perform their intended function.


Chimney Problems to Avoid

Oil and gas furnaces have distinct burning characteristics and produce different combustion by-products. However, the chimneys and connector pipes that serve them share common problems. Both systems are subject to weathering, animal invasions, deterioration and rust-out and the accumulation of nest materials and debris. Both require regular care and maintenance.

Oil flues need to be cleaned and inspected annually because deposits of soot may build up on the interior wall of the chimney liner. The amount of soot depends on how well-tuned the furnace is and whether the house provides sufficient air for combustion. Excessive soot causes problems that range from chimney fires … to flue deterioration … to chimney blockages that direct toxic fumes back into the house and cause inefficient furnace operation. See the brochure from the CSIA specifically relating to oil-burning appliances.

 Natural gas is a clean-burning fuel, but today’s high-efficiency gas furnaces pose a special problem. The fumes they produce are cooler and contain high levels of water vapor, which are more likely to cause condensation than older models. Since these vapors also contain chlorides picked up from house-supplied combustion air, the flues are subjected to more corrosive conditions than before.

Even worse, many gas appliances use chimneys that once served oil furnaces. If the liners of these chimneys are made of terra cotta (fired clay commonly used in chimney construction), bits and pieces of them slowly flake off under corrosive conditions. The combination of water-laden gas vapors available to mix with old oil soot deposits speeds this process, and debris that can block the chimney builds up at the bottom of the flue.

To the extent that problems with either of these heating systems interfere with the flow of toxic gases and particles out of the house, they may also force carbon monoxide, fumes and possibly soot into the living spaces of your home. They may cause a one-time, high-level exposure situation or release smaller amounts more regularly over a longer period. These problems should never be ignored.

Preventing Problems

In the United States, numerous agencies and organizations now recognize the importance of annual heating system inspection and maintenance in preventing carbon monoxide poisoning. The U.S. Consumer Product Safety Commission, the U.S. Environmental Protection Agency, the National Fire Protection Association, and the American Lung Association – are some of the organizations that now encourage the regular maintenance of home heating systems and their chimneys in order to keep “the silent killer” at bay.

A well-tuned furnace or boiler – connected to a venting system or flue that is correctly-sized, structurally sound, clean and free of blockages – will operate efficiently and produce a warm and comfortable home. An overlooked heating system can produce death and heartbreak.

Considering the risks involved when gas or oil systems are neglected – and the benefits that accrue when they are properly maintained – you would do well to have your chimneys checked annually by a CSIA Certified Chimney Sweep® and swept or repaired as needed. This can keep illness or death from carbon monoxide poisoning from claiming you or those you love.

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