Buying guide · Air monitors
The best CO₂ monitors for home, bedroom and classroom
Our top picks: the Aranet4 Home, the Qingping CO₂ & Temp & RH Monitor and the Qingping Air Monitor 2. CO₂ is the tell-tale of stale air. Every breath adds it, so in a shut room it climbs, and a monitor shows when to open up. On a smoggy day that's the trade-off: keep the smog out, but air the room at the cleanest hour.
Only NDIR sensors measure CO₂ itself; cheap 'eCO₂' sensors estimate it from other gases. Every pick here uses NDIR.
Updated · 6 picks · figures from AHAM, Energy Star, NIOSH and the makers · no brand pays to be listed
Our 6 picks at a glance
Aranet4 HomeFresh-air check
$189.00at aranet.com
Amazon(opens in a new tab)
Qingping CO₂ & Temp & RH MonitorWi-Fi CO₂
$69.99at qingping.co
Amazon(opens in a new tab)
Qingping Air Monitor 2Best overall
$149.99at qingping.co
Amazon(opens in a new tab)
Temtop M2000 (2nd gen)Handheld
$209.99at temtopus.com
Amazon(opens in a new tab)
IQAir AirVisual ProIndoor vs outdoor
$329.99at iqair.com
Amazon(opens in a new tab)
Qingping Air Monitor LiteApple Home
$76.00at qingping.co
Amazon(opens in a new tab)
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Fresh-air check
Aranet4 Home
The accurate one: NDIR within ±(30 ppm + 3%), years on two AA batteries.
$189.00at aranet.com
Wi-Fi CO₂
Qingping CO₂ & Temp & RH Monitor
NDIR with Wi-Fi alerts, at a lower list price.
$69.99at qingping.co
Handheld
Temtop M2000 (2nd gen)
A handheld SenseAir NDIR meter that also reads particles and formaldehyde.
$209.99at temtopus.com · sale price, was $229.99
Indoor vs outdoor
IQAir AirVisual Pro
CO₂ and PM2.5 with the outdoor reading beside them.
$329.99at iqair.com
How we chose
NDIR sensor
Measures CO₂ directly, unlike eCO₂ estimates.
Easy to read
A color light or clear screen that says 'open a window' at a glance.
Fits how you'll use it
Battery for moving room to room; Wi-Fi for alerts on your phone.
We haven't lab-tested these ourselves. The rankings rest on independent ratings (AHAM's verified CADR, Energy Star's listings, NIOSH approvals) and the makers' own figures, each shown on the product's page with where it's from. No brand pays to be listed, and the order doesn't change with commission. We earn a small commission when you buy through our links.
Questions
- What is a good CO₂ level indoors?
- Outdoor air is about 420 ppm. Indoors, under about 1,000 ppm means the room is well ventilated; above about 1,400 it's time to air it.
- What's the difference between NDIR and eCO₂ sensors?
- NDIR measures CO₂ by how it absorbs infrared light. eCO₂ sensors measure other gases and estimate CO₂ from them, which can be far off.
Before you buy
Check how bad the air gets where you live
A purifier matters most where the air is often unhealthy. See today's reading and the past week for your city, from the nearest ground stations.