What Is Indoor Air Quality?
Indoor air quality (IAQ) refers to the condition of the air inside buildings as it relates to occupant health and comfort. We spend roughly 90 percent of our time indoors, yet indoor air can be two to five times more polluted than outdoor air. IAQ encompasses several key pollutants and environmental factors.
The Key IAQ Metrics
Carbon Dioxide (CO2)
CO2 is the most accessible indicator of ventilation adequacy. Levels above 1,000 ppm signal that fresh air supply is insufficient. Our complete PPM guide explains the ranges in detail.
Particulate Matter (PM2.5)
Fine particles smaller than 2.5 micrometres penetrate deep into the lungs and bloodstream. Sources include cooking, candles, wildfires, and outdoor pollution infiltration. Learn how PM2.5 compares to CO2 in our PM2.5 vs CO2 comparison.
Volatile Organic Compounds (VOCs)
Off-gassing from furniture, paint, cleaning products, and building materials releases VOCs. Some are harmless, others are carcinogenic. Read our VOC monitoring guide for more.
Humidity
Ideal indoor relative humidity is 40-60 percent. Too low and you get dry skin and respiratory irritation; too high and mould thrives. See how temperature and humidity affect IAQ.
Temperature
Thermal comfort affects perceived air quality. Most people are comfortable between 20-24 degrees Celsius.
How to Start Monitoring
- Begin with CO2 — it is the easiest and most actionable metric. A good NDIR monitor costs $80-$250.
- Add PM2.5 — especially important if you cook with gas, burn candles, or live near wildfire-prone areas.
- Consider a multi-sensor unit — devices like the Airthings View Plus cover CO2, PM2.5, VOCs, humidity, and temperature in one package. See our home monitor recommendations.
- Track trends — single readings are less useful than patterns over days and weeks. Our guide on reading your monitor data helps you interpret the numbers.
Use the CO2 calculator to get a baseline understanding of your space before purchasing.