Some of the biggest potential impacts on indoor air quality (IAQ) come from combustion appliances. It’s a huge topic, but let’s focus on the essentials here. I’ll discuss the basic problems along with specifics for different types of combustion appliances.

Three types of problems

The first thing to know is that there are three ways that combustion appliances can affect IAQ.

1. Fuel problems. It could be anything related to the fuel being used: gas leaks, oil spills, coal dust, mold growing on wet wood brought into the house. Talk to people who test a lot of homes for gas leaks, and you’ll hear some scary numbers, like 80 or 90% of the homes they test have gas leaks.
2. Combustion problems. The products of combustion you get depend on the process of combustion. If the fuel is clean and burns completely, the exhaust gases are cleaner.
3. Venting problems. Not all combustion appliances vent the exhaust gases to outdoors. Even some of those that do allow for spillage.

I covered these problems in a bit more detail in an article on combustion safety.

Gas cooktops and ovens

The biggest source of fine particles (particulate matter 2.5 microns and smaller, PM2.5) in many homes is cooking. And the biggest reason they create an IAQ problem in the home is that people just don’t turn on the range hood. Lawrence Berkeley National Laboratory (Berkeley Lab) found that about a third of the people use their range hood infrequently and another 10% never turn it on.

And then there are homes like the one below, where there’s no range hood to turn on when cooking. As you can see, the walls and ceiling catch some of the pollutants. The rest float around in the indoor air, being breathed by anyone in the house.