Last updated on July 21, 2025
There are a few different types of air sensors
- Particulate matter (PM) sensors
- Gas (Ozone, Carbon monoxide, Nitrogen dioxide, Sulfur dioxide) sensors
- Total VOC (volatile organic compound) sensors
PurpleAir sensors are particulate matter sensors and measure PM2.5, particulate matter up to 2.5 micrometers in length. That’s particles smaller than the width of a strand of human hair! Read in Criteria Air Pollutants about the health effects of PM2.5.
As described by the EPA…
Currently, PM is typically measured using an optical approach where light scattered by a particle(s) is used to estimate the particle mass concentration. The amount of light scattered can vary due to the size, shape, and chemical composition of the particles. This method can only detect a narrow range of particle sizes. Over time, particles may build up within the sensor causing changes in performance. Lifetimes vary but are often between 1 to 4 years. PM sensors are typically useful for outdoor, indoor, and smoke monitoring applications. Currently, many sensors will not detect PM10 or dust.
In short… PM sensors use light to determine the size, shape, and type of particles that pass through them. They then use that information to determine the concentration (how many of the particle are in the air) of PM2.5.
As seen in the diagram below, air flows through the sensor, is analyzed within the sensor, then flows out of the sensor.
Be First to Comment