Backdrafting can be dangerous to the health of those who occupy a building, so knowing about it and fixing it are very important.
For inspectors, the most simple test involves releasing smoke into the draft diverter to see what happens. Using a chemical puffer or smoke pencil, the smoke will either get sucked into the duct or get pushed backwards the way it came. Furthermore, many inspectors use a lighter to see whether the flame is pulled into the duct and general direction of the flue.
To test for gas in a particular room, a carbon monoxide analyzer can be used but this requires knowledge of the equipment otherwise false negatives can be returned. Also, there should be evidence of the gases coming back through the system because it normally results in dark residue which can be spotted by the inspector. Whenever there is soot, it suggests that backdrafting has or is occurring so further investigation will be required. However, this doesn’t give a cut and dry answer because not all cases have this residue – therefore, it is simply seen as an indicator either way.
During the tests above, the inspector is likely to ask homeowners to turn all devices on to see what happens. For example, kitchen fans or dryers may be put into action to simulate a regular day. While not part of a typical home inspection, please feel free to ask us about this.
