Air Quality Sensors
The IAQ supports three different air quality sensors for detecting specific types of indoor pollutants. You can use any combination of the sensors depending on your budget and air quality needs. The types of pollutants are detailed below, but for specific sensor information such as model and cost, see our hardware guide.
Carbon Dioxide (CO2)
CO2 is an odorless, colorless gas that is a natural component of the air that we breathe. The amount of CO2 in our air is usually expressed in parts per million, or ppm. Outdoor air in most locations has as little as 380 ppm of CO2. People exhale CO2 therefore it has the potential to accumulate indoors when ventilation is inadequate.
Various guidelines exist for the recommended limit of CO2 concentrations indoors, so the IAQ uses an average of these with 1,000 ppm indicating moderate levels, resulting in an IAQ score of 50 and the LED turning yellow. For more details, see the docs for the IAQ score.
Particulate Matter (PM)
PM is a mixture of substances suspended in the air as small liquid and/or solid particles. Examples of this include dust, smoke, and smog. Particulates are considered one of the most harmful forms of air pollution due to their ability to penetrate deep into the lungs, blood streams and brain, causing various health problems.
The PM sensor used in the IAQ (like the one found in many consumer, sub-$400 devices) is most accurate at detecting fine particulate matter known as PM2.5 - these particles, such as vehicle exhaust and combusted fossil fuels, are 2.5 microns in size or smaller. It also provides an estimation for PM10, which which is a measurement of slightly larger particles. The chart below illustrates this range:
(source: Jisaac9, Mieszko the first, CC BY-SA 3.0, via Wikimedia Commons, modified)
The IAQ utilizes EPA guidelines for setting PM limits, with concentrations of 35.0 µg/m3 and 54.0 µg/m3, for PM2.5 and PM10 respectively indicating moderately unhealthy indoor air quality. For more details, see our docs about the IAQ score.
Volatile Organic Compounds (VOC)
Volatile organic compounds are chemicals that include those produced by fossil fuel use and production, solvents used in coatings, paints, and inks, compressed aerosol products, and cooking oil combustion. Health effects include eye, nose, and throat irritation; headaches, loss of coordination, nausea; and damage to the liver, kidney, and central nervous system, among others. The ability of organic chemicals to cause health effects varies greatly from those that are highly toxic, to those with no known health effects. As with other pollutants, the extent and nature of the health effect will depend on many factors including level of exposure and length of time exposed.
The IAQ includes a gas sensor that can detect a wide range of Volatile Organic Compounds, and is able to provide a good idea of trends and comparison VOC levels for indoor air. It also allows for a calibration procedure when first powered on. For more details, see our hardware guide.
