Particulate Matter (PM)
Type: Near infrared Nephelometer
Range: 0-50 ug/m3
Theory of Operation: A light beam and a photo detector are focused at a shared point in a small chamber. A fan, mounted at the back of the monitor, pulls air through this chamber. Particulate matter between .7 and 10 microns, is measured as it is suspended in this air stream scatters light from the beam, triggering the photo detector. The signal from the photo detector is monitored and an overall particulate level is calculated.

Carbon Monoxide (CO)
Type: Electrochemical
Range: 0-100 ppm
Theory of operation: Exposure of the sensor to carbon monoxide gas produces a signal that is proportional to the concentration of the gas. This signal is recorded and converted to CO in ppm.

Temperature
Type: Thermal Resistor (Thermistor).
Range: 32-100 Degrees F
Theory of operation: Resistance of the sensor changes in proportion to changes in temperature. This resistance change is converted to temperature in Degrees F.

Relative Humidity (RH)
Type: Capacitive
Range: Range 10-90%
Theory of operation: Moisture changes the capacitance of the sensor, which is measured and converted to relative humidity in % RH.

Total Volatile Organic Compound (TVOC)
Type: Metal Oxide Semi-Conductor (MOS)
Range: 0-4000 ug/m3
Theory of operation: Conductivity of the sensor changes in the presence of detectable gases. The sensor in the AirAdvice IAQ Monitor was chosen due to its high sensitivity to gases common in office and home environments. AirAdvice calibrates the TVOC sensor using Isobutylene, a common reference gas.

Carbon Dioxide (CO2)
Type: Non-dispersive infrared (NDIR)
Range: 0-2000 ppm
Theory of operation: Carbon Dioxide, like most molecules, absorbs infrared light at a unique wavelength. The sensor has a lamp and infrared detector designed to work at this unique wavelength. Air with a high level (concentration) of CO2 absorbs more light at this wavelength than air with a low level of CO2. This light absorption is measured and converted into a CO2 concentration.

Note: Data from various sensors are corrected for environmental conditions (temperature, relative humidity and barometric pressure) as necessary.