Use an air quality monitor or sensor
Measure PM2.5 and PM10
Measure carbon monoxide
Measure carbon dioxide
Measure nitrogen dioxide
Measure ozone
Measure sulfur dioxide
Measure volatile organic compounds
Check temperature and humidity
Compare readings to air quality standards
Monitor indoors and outdoors
Take measurements at different times of day
Record and track changes over time
Calibrate devices regularly
Use official air quality index data when available