Most advice about indoor air quality starts in the wrong place. It hands you a monitor to buy before you have worked out what is even worth measuring, and what to measure for indoor air quality depends far more on how and where you live than on whichever device is trending this month. Since this is probably the question I get asked the most, I designed this tool to help simplify the process.
Describe your home
Tick the sources indoors, the building itself, the air outside and who lives there.
See your priorities
The tool ranks the pollutants that matter for you and groups them by how you would measure each one.
Know what to buy
Every result names the sensor to look for and the catch to avoid.
Tick what matches your home and your habits below. The answer updates as you go, and nothing you select ever leaves your browser.
Most of these fit in one box. Some do not.
This tool sorts the pollutants you care about into three groups: the ones that are easy to find together in a multi-pollutant device, the ones that need their own dedicated kit, and the ones no affordable sensor measures well.
What your air quality monitor actually measures
Two monitors can both claim to measure “CO2” while only one of them really does. A genuine reading comes from an NDIR sensor; plenty of cheaper devices report eCO2 instead, a guess worked out from a VOC sensor that can drift badly. PM10 is often inferred from the PM2.5 reading rather than measured separately. Proper nitrogen dioxide and ozone sensors are expensive and almost never included in consumer monitors, and the NOx index from parts like the Sensirion SGP41 is not a true NO2 reading. Where it matters, the tool tells you which sensor to look for, so you can check what a device actually measures before you trust its readings.
Sometimes you need a test, or an alarm
Carbon monoxide is a life-safety matter, so it needs a certified alarm built to your country’s standard, UL 2034 in the US or EN 50291 in the UK and EU, not a graph that will not wake you at night. Radon swings from day to day, so it wants a long-term test rather than a live number; the US EPA advises acting at 4 pCi/L (about 148 Bq/m³), while the World Health Organization uses a lower reference of 100 Bq/m³. And where no affordable sensor exists, cutting the source beats chasing a number you cannot trust. Your air is not fixed either, so it is worth running the questions again whenever your home or your habits change.
Start here
CO2 monitors
What a good CO2 reading looks like, NDIR versus cheaper sensors, and which monitors to trust.
Read the guide →Air quality monitors
PM2.5, VOCs and the rest: how the sensors work, and what they can and cannot tell you.
Read the guide →Radon monitors
Why radon matters, short versus long-term testing, and the detectors worth owning.
Read the guide →