PPM is an absolute measurement, whereas mg/m3 varies depending on pressure and temperature. Handheld monitors measure in ppm and apply a conversion factor if you want to measure in mg/m3. The following table shows the conversion factor for each sensor head.
|Sensor||PPM conversion to mg/m3|
|Volatile organic compounds||2.5|
Because particulate matter varies in size (unlike a gas molecule), ppm isn’t a valid unit of measurement. Therefore, the true unit for the PM measurement is always in mg/m3.
You can’t change the conversion factor on the sensor head or within the Series 500 software. To apply a different conversion factor, log your data in ppm, use the Series 500 software to download and export the data to an Excel spreadsheet, and then calculate mg/m3 readings using a different conversion factor.