Carbon Monoxide (CO) monitoring
These can affect humans by causing low level symptoms such as headaches, nausea and dizziness leading up to vomiting and loss of mental/muscular control at high exposure and death in extreme cases.
Carbon monoxide as a pollutant is found in the ambient air as well as stack and naturally in background measurement. Carbon monoxide is a requirement for most ambient air monitoring projects including being one of the 6 criteria pollutants required for measurement by the U.S. EPA. Carbon monoxide is often measured in conjunction with Carbon Dioxide for Carbon emissions monitoring.