The easiest way to check if your house is encapsulating gases is to monitor the carbon dioxide (CO₂) levels. This one gas is used as a marker for air quality, is the easiest to monitor, and provides a more accurate air quality reading.

It is a good trend indicator because it changes in measurable amounts as the air quality gets worse. All other gasses in the house follow the same trend as the CO₂. Most commercial air quality controls are based on CO₂ levels.

It is the easiest to monitor simply because as the air quality gets worse, the levels increase. Outside air has an average of 350 – 450 ppm of CO₂. Inside, the levels raise to values of 550 – 700 ppm. In office buildings, the HVAC systems will keep the levels below 800 ppm.

Monitoring the CO₂ levels is relatively inexpensive and more accurate compared to monitoring any of the other gases that are in your home such as carbon monoxide (CO) and TVOC. It is more accurate in that it does not change based on individual problems.

CO Monitors

CO monitors are commonly sold at the local hardware store. The problem with CO monitors is that it always reads 0 ppm. This reading does not mean that you are safe because it is only looking for the CO gas that is produced by cars and things that are burning. The reason CO monitors are so common is that a large part of the world uses natural gas to cook their food and if this gas is not burned correctly it can produce CO. This monitor does not tell you what your air quality is. It is used for a specific purpose which is to detect CO.

TVOC Monitors

TVOC monitors are expensive and can cost thousands of dollars. You would think you are safe because it always reads less than 0.04 ppm. If you just purchased a new desk that is manufactured in a country that is not regulated, you will see an increase in your TVOC values but how do you know which type of VOC it is? Within a week or two, the levels will then return to values of about 0.05 ppm. This may take several months to a couple of years for the VOCs to stop off gassing from the desk and return to less than 0.04 ppm. It’s impossible to say the increase or decrease was due to formaldehyde or hydrogen sulphide. It’s also impossible to identify what combination of VOC made up the TVOC reading.

CO₂ Monitors

CO2 monitor is like a smoke detector and looks at the general problem. If a smoke detector only went off if the fire was caused by burning macaroni and cheese it may save your life but the odds are lower than if it detects all the source of fire. The CO₂ monitor does not detect all the source of poor air quality but it tells you if you are in a location that has poor air quality or even bad air quality and this means the levels of all the gases that can have effects on your quality of life are higher.

Written by: Richard Grant, Service Department Supervisor