Common Indoor Pollutants and Their Sources
Indoor air quality work starts with knowing what you are actually looking for. The pollutants you will encounter most often fall into a few groups, and each has predictable sources you can trace during a walkthrough.
Particulate matter (PM) is solid and liquid material suspended in the air. PM10 includes coarser dust and pollen, while PM2.5 is fine particulate that lodges deep in the lungs. Sources include cooking, candles, smoking, wood stoves, unfiltered outdoor air, and resuspended dust from foot traffic.
Volatile organic compounds (VOCs) are gases released by paints, adhesives, cleaning products, new flooring and furniture, air fresheners, and fuel. Symptoms like headaches or eye irritation often track with VOC sources.
Carbon dioxide (CO2) is not toxic at indoor levels but is a reliable proxy for ventilation: when many people occupy a poorly ventilated room, CO2 climbs. Carbon monoxide (CO) is a separate, dangerous gas from combustion appliances, attached garages, and backdrafting flues.
Finally, humidity is a pollutant driver: too high and you invite mold and dust mites, too low and you get irritation. Knowing the source category for each reading is what lets you recommend a fix rather than just report a number.