"Breath carbon monoxide is the level of carbon monoxide in a person’s exhalation. It can be measured by testing using a carbon monoxide breath monitor (breath CO monitor). This test is designed for smoking cessation and as a clinical aid in assessing carbon monoxide poisoning.
CO monitors measure carbon monoxide in parts per million (ppm) in breath. The tests are increasing in popularity because they are noninvasive and are inexpensive to use."