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PM2.5, CO2, VOC and radon monitors, and how far to trust their sensors.
A nursery monitor is most useful for temperature, humidity and ventilation, with PM2.5 as a bonus. It does not replace a smoke or CO alarm. Here is what to track and what to buy.
A home monitor is a bundle of small sensors, each good at one thing. Knowing which sensor sits behind each number tells you which readings to trust and which to treat as a trend.
The View Plus is the most complete home air monitor Airthings makes: radon plus particles, CO2 and VOCs, on batteries or USB-C. It is expensive, and worth it mainly if you want radon too.
The Wave Enhance is Airthings' small, battery-powered monitor for bedrooms and offices. Unlike the old Wave Mini, it measures CO2 with an NDIR sensor. It does not measure radon or particles.
The Wave Plus does the two jobs most homes care about after particles, radon and ventilation, in a battery-powered disc you can mount on a wall. It skips PM2.5, and costs less for it.
The Atmotube PRO 2 clips to a bag and measures particles, CO2, VOCs and NOx wherever you go. Its predecessor tested well for particles in South Coast AQMD's program; the PRO 2 adds CO2.
The Awair Element looks better than most monitors and measures the five things most people care about. It is sold through Awair rather than Amazon, and independent accuracy data is thin.
The Awair Omni is built for offices and buildings, with a dashboard for fleets of monitors and RESET accreditation. In a home, you pay for features you will not use.
CO2 tells you how well a room is ventilated. Only an NDIR sensor measures it directly. These monitors use one, and we explain what the readings mean for a bedroom or office.
A continuous radon monitor shows your short- and long-term averages without lab fees. These are the best we found, and how to use one alongside the EPA's test-then-confirm advice.
Some home monitors track a reference instrument closely; others barely at all. Here are South Coast AQMD's independent PM2.5 results by model, and what makers' accuracy claims really cover.
The AirVisual Pro's strength is context: it shows your indoor PM2.5 and CO2 next to outdoor air from IQAir's network. Independent field results were more modest than cheaper rivals, and it is pricey.
The PurpleAir Flex is built to hang outside and feed the public PurpleAir map. It is a good outdoor particle sensor with independent test results. For indoor monitoring, PurpleAir points to other models.
The Qingping Air Monitor Lite is cheap, reads particles and CO2, works with Apple Home, and did well in South Coast AQMD's independent field test. It has no VOC or radon sensor and needs to stay plugged in.
The M10+ is Temtop's current M10: a cheap, battery-friendly e-ink monitor for CO2, particles and VOCs. It is a sensible bedroom or desk monitor; just do not expect lab-grade numbers.
A monitor is only as good as its sensors. We picked the ones with laser particle sensors, true NDIR CO2 and, where it exists, independent accuracy testing from South Coast AQMD.
New paint, flooring, cabinets and furniture all release VOCs. A monitor shows the trend and whether ventilation is working; EPA's steps (ventilation, moderate heat and humidity, certified wood products) do the work.
Put the monitor where people breathe, not where air blows. Breathing height, a few feet from windows, vents and the stove, and, for radon, EPA's lowest-lived-in-level rule.
