A purifier’s work shows up as falling PM2.5, and a monitor is how you see it happen in your own room. We only list monitors whose readings South Coast AQMD’s AQ-SPEC program tested against reference instruments, and whose tested model is still the one on sale.
Qingping
A palm-sized desk monitor for PM2.5, PM10, CO2, temperature and humidity, with Wi-Fi and Apple Home support. South Coast AQMD's AQ-SPEC program tested its PM2.5 readings outdoors and in a chamber against reference instruments.
Temtop
A handheld meter for PM2.5, PM10, CO2, formaldehyde, temperature and humidity that exports its readings over USB. South Coast AQMD's AQ-SPEC program tested its PM2.5 readings outdoors and in a chamber against reference instruments.
| Monitor | PM2.5 outdoors (R²) | In the chamber | Also measures | Connection |
|---|---|---|---|---|
| Qingping Air Monitor Lite | 0.85–0.93 | Reads 18–32% low from 14.6 µg/m³ up | PM10, CO2, Temperature, Humidity | Wi-Fi 2.4 GHz, Bluetooth 5.0 |
| Temtop M2000 2nd Generation | 0.77–0.82 | Reads 30–45% high at every level tested | PM10, CO2, Formaldehyde, Temperature, Humidity | Export over USB |
R² describes how closely readings tracked the reference: 1 is perfect. The field rounds ran in different seasons, so compare them loosely. The chamber column says which way each monitor’s numbers lean.
Why a monitor belongs next to a purifier
In a room of the size AHAM suggests for it, a purifier running at its rated smoke CADR should roughly halve PM2.5 every nine minutes once the source stops. Any monitor on this page can show you whether yours does.
Run the testFrom AQ-SPEC’s particulate matter sensor summary, checked in September 2026. A monitor missing from those published results says nothing either way about how accurate it is; it only means there is no independent result to check it against.
It can show a trend, but it measures air at the machine itself, not on the far side of the room. EPA’s technical summary on residential air cleaners also notes that it found no studies of how those built-in sensors perform over time. A separate monitor placed across the room is the fairer check.
The map describes outdoor air, usually as an index built from recent averages, while your monitor reads the room right now in µg/m³. Low-cost sensors are also biased: in AQ-SPEC’s chamber the Qingping Air Monitor Lite read about a quarter to a third low and the Temtop M2000 2nd Generation 30–45% high. For checking a purifier, how fast the reading falls matters more than the number itself.
No. CO2 is a gas and a particle filter captures particles; EPA’s technical summary on air cleaners covers gas removal as a separate technology. What lowers CO2 is ventilation, so a CO2 reading tells you when a room needs fresh air, not whether the purifier is working.
