Energy & Sustainability
How to read basic air quality sensor readings
A practical guide for anyone looking at a small air sensor dashboard for the first time. It covers what to look at, how to judge a number and when to act on it.
01
Step one: identify the pollutant and unit
Start by finding which measurement you are seeing. Many small sensors report fine particles, often labeled PM2.5, in micrograms per cubic meter, and some add a combined index number. These are not interchangeable, so note the label and unit before comparing anything. Worked example: a sensor in a classroom shows PM2.5 at 12 and an index color of green. Write down that the pollutant is fine particles, the unit is micrograms per cubic meter, and the reading is a single moment rather than an average. That note anchors every later comparison.
02
Step two: compare against a reference and a trend
A single number means little without context. Check the reference bands your sensor or local agency publishes, and look at the last several hours of readings. In the classroom example, a value of 12 sits in a low band, but if the trend shows it was 4 an hour ago, something changed. Ask what happened: a door opened, cooking started, or smoke arrived from outside. Compare with an outdoor reading if available. The shape of the line, rising, flat or falling, often tells you more than the instant value on its own.
03
Step three: decide on a small action and recheck
Turn the reading into a modest, reversible decision. If the classroom number is rising, close windows facing a busy road, run a filter if one exists, and note the time. Then recheck after fifteen to thirty minutes to see whether the line responds. Keep a short log of reading, cause and action so patterns emerge over weeks. Remember that low-cost sensors can drift or read high in humid air, so treat results as indicators and confirm important concerns with official monitors or qualified professionals before drawing firm conclusions.