Carbon monoxide (CO) is one of the products of combustion. Specifically, it is formed when combustion is not perfect. CO is an odorless, tasteless, invisible gas which is poisonous humans. For this reason it is called the silent killer, and CO poisoning has become more frequent as the building envelope has been tightened. With less fresh air available in newer construction, the risk of CO poisoning increases.

CO is typically produced at a combustion appliance such as a furnace or water heater, and can be distributed through the house due to faulty heat exchangers, or back drafting of the appliance. Once in the house air, we can breathe in the CO, and as the concentration increases, the severity of the poisoning likewise increases.

Typical residential CO detectors should be installed on any floor where people sleep, and alarm at 100 parts per million (ppm). The CO detection equipment we use will find concentrations down to 1 ppm. Every house we inspect has this test performed; we find failure in new and old homes.