Heating Season is Here–If you have a combustion heater, make sure your chimney is working right!

HVAC systems are hard-working in extreme climates, and very often taken for granted.  The thought is: If it worked fine last winter, why mess with it?  The fact is, every combustion heater (gas, oil, wood, coal, etc.) has “byproducts” of combustion that slowly build up inside and/or corrode the chimney.  Every year that it’s not checked could be a year where a blockage or leak forms, exposing you and your family to harmful gases like carbon monoxide.  

First of all, definitely get your chimney checked by a professional if there is any work done in that area.  As an amateur DIY person who helps out when she can, I was horrified to discover that after workers replaced part of my friend’s roof, they had disconnected and roofed over the exhaust gas vent of her hot water heater, causing the combustion gases to be released inside the home!!  Although she didn’t use a lot of hot water (it was during the summer), just having the pilot light lit without an exterior vent allowed gases to accumulate in her home and caused her to feel ill.  

The Chimney Safety Institute of America (CSIA) has a very helpful Q & A page about combustion appliances and how they work.   Even though gas furnaces are very efficient, they do create water vapor, which when combined with the exhaust fumes corrodes the piping or liner of the exhaust flue.  According to this authority, there are 3 main causes of damages to chimneys that vent oil-fired appliances:  

1. The acidic nature of the byproducts of combustion (see above).

2. A mismatch in flue/appliance size: sometimes when replacing or upgrading your furnace, the exhaust vent piping does not match that required for the new furnace.  “For example, where an old unit may require an eight-inch flue, the new replacement unit’s installation instructions may call for a five-inch flue. This is a 60% reduction in flue size. If the flue isn’t relined to accommodate the new appliance, you’ll likely experience issues with draft, performance, efficiency, and carbon monoxide.”

3. Lower flue gas temperatures:  more efficient appliances tend to have lower exhaust temperatures as well, which approach the dew point and can cause corrosion issues. 

These are all reasons to call a CSIA-Certified Chimney Sweep® to evaluate your chimney whenever you replace your appliance, and also on an annual or semi-annual basis during use to inspect it.  This is especially true if you have a wood- or coal- burning stove, which produce more particulates as they burn.

The other thing that deserves great attention are the fresh air intake ducts, which supply combustion air to the furnace or water heater.  This video shows where you may find them and how to clean (we would suggest a vacuum, however, instead of a toothbrush, so that the dust doesn’t go into the ducts).  The reason it can cause carbon monoxide to accumulate in your home is because as the vent gets plugged, there is insufficient air for the gas furnace to burn cleanly, and insufficient “draft” to move the exhaust gases up the exhaust flue.  

It’s super-important to have a carbon monoxide detector in your home if you have a gas-burning appliance.  

There are signs of problems with your furnace exhaust vent piping.  These include:

• Headaches, nausea, dizziness, and fatigue… carbon monoxide is odorless, so you will not know what is causing these symptoms!

• Problems due to increased water vapor in your home (the average furnace puts out about 1.5 gallons of water in the chimney every hour it’s used, and if the water vapor can’t escape via the exhaust vent piping, it goes into your home!): 

• Damp patches on interior walls or exterior walls

• Peeling wallpaper

• Blistered paint

• Stains on the ceiling

• Moldy areas  

• Water leaking from the flue pipe

• White stains (efflorescence) on the outside of the masonry chimney

• Eroded mortar joints or crumbling bricks on the chimney

Gas appliances are one area where you don’t want to take a chance on “I think I’ve got it right” because an undetected exhaust gas leak can be deadly.  This link can help you find a certified professional in your area.

Photo by Luis Felipe Lins on Unsplash