Indoor Air Quality Monitors

A multi-sensor indoor air quality monitor tracks several pollutants at once, typically PM2.5, CO2, total VOCs, temperature and humidity, and shows trends in an app. Sensor type matters more than the number of readings, so check what each reading is based on.

What to compare

• CO2 sensor: NDIR measures actual CO2. "eCO2" is an estimate from a VOC sensor and is far less reliable.
• PM2.5: laser particle sensors are standard. Check whether the brand publishes accuracy figures.
• VOCs: metal-oxide sensors show relative changes, not specific chemicals.
• Display vs app-only: a screen is handy for quick checks without your phone.
• Power: battery models are flexible, while plug-in models can sample more often.
• Integrations: some connect to smart home systems or trigger a purifier.

Compare Smart Air Quality Monitors with Wi-Fi alerts, or Airthings Monitors, which add radon sensing.

FAQs

What does an indoor air quality monitor measure?

Most measure fine particles (PM2.5), carbon dioxide, total volatile organic compounds, temperature and humidity. Some add PM10, formaldehyde, nitrogen dioxide, air pressure or radon. The quality of each reading depends on the sensor technology, so check whether CO2 uses an NDIR sensor and how PM2.5 is measured.

Is eCO2 the same as CO2?

No. eCO2 or equivalent CO2 is calculated from a VOC sensor's reading, using an assumed relationship between people's emissions of VOCs and CO2. It can be far off from real CO2. NDIR sensors measure CO2 directly by how it absorbs infrared light, and are the standard for reliable readings.

Can an air quality monitor detect mold?

Not directly. Monitors cannot identify mold, but high humidity readings above about 60% show conditions where mold can grow, and some VOC sensors may react to musty odors. If you suspect mold, look for moisture sources and visible growth, and follow EPA guidance on cleanup.