Common pollutants tested are volatile organic compounds (VOCs), mold spores, particulate matter, carbon monoxide (CO), radon, and formaldehyde. Testing methods include air sampling, surface sampling, and direct-reading instruments. Health implications of extremely poor air quality can include respiratory issues (poor air quality can exacerbate conditions like asthma, bronchitis, and allergies), headaches and fatigue (exposure to VOCs and other pollutants can cause headaches, dizziness, and fatigue), and serious health risks (long-term exposure to high levels of certain pollutants, such as radon and formaldehyde, can lead to serious health issues, including cancer).