Aranet · Fresh-air check
Aranet4 Home
An accurate CO₂ meter that tells you when a shut room needs fresh air: the trade-off to watch while you keep smog out.
- NDIR CO₂ sensor, ±(30 ppm + 3%)
- Runs for years on two AA batteries
$189.00at aranet.com · Nov 2026
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Aranet4 Home at a glance
- Measures
- CO₂, temperature, humidity, air pressure
- CO₂ sensor
- NDIR, 0–9,999 ppm, ±(30 ppm + 3%)
- Indicator
- Colour light: green below 1,000 ppm, yellow to 1,400, red above
- Screen
- E-ink, readable in daylight
- Battery
- 2 × AA, up to about 4 years
- App
- Bluetooth, with up to 90 days of history
From the maker
Our take
Shutting windows against smog has a cost: the CO₂ we breathe out builds up, and a closed bedroom can climb well past 1,000 ppm overnight. The Aranet4 tells you when that's happening, so you can air the room for a few minutes at the cleanest time of day.
Its NDIR sensor is the accurate kind, and two AA batteries last for years. It doesn't measure particles: pair it with a purifier's sensor or a PM2.5 monitor.
It doesn't measure particles (PM2.5).
Good for
- Bedrooms, classrooms and offices kept shut against smog
- Anyone who wants an accurate CO₂ reading without a cable
Skip it if
- You want to see PM2.5: it doesn't measure particles
How it compares
Every air monitor in the shop.
| Product | Best for | Price |
|---|---|---|
| Qingping Air Monitor 2 | Best overall | $149.99 |
| Aranet4 Home (this one) | Fresh-air check | $189.00 |
| Airthings View Plus | Radon too | $329.99 |
| IQAir AirVisual Pro | Indoor vs outdoor | $329.99 |
| Qingping Air Monitor Lite | Apple Home | $76.00 |
| Temtop M2000 (2nd gen) | Handheld | $209.99 |
| GoveeLife Smart Air Quality Monitor H5106 | Budget PM2.5 | $39.99 |
| Qingping CO₂ & Temp & RH Monitor | Wi-Fi CO₂ | $69.99 |
Goes with
Qingping CO₂ & Temp & RH MonitorWi-Fi CO₂ · $69.99
In our buying guides
Head to head
Questions about the Aranet4 Home
- Why measure CO₂ on a smoggy day?
- Keeping windows shut lets the CO₂ we breathe out build up, and the room turns stuffy. Aranet4 shows when to air it, so you can do it at the cleanest time of day.
- How long do the Aranet4 batteries last?
- Aranet rates two AA batteries at up to about 4 years, measuring every 10 minutes without a phone connected. Shorter intervals use them faster.
How we judge. We haven't tested the Aranet4 Home in a lab of our own. The figures come from independent ratings (AHAM, Energy Star, NIOSH, the ASPCA) or the maker, and the verdict is ours, from those figures. No brand pays to be listed. Last checked Nov 7, 2026.
Aranet4 Home
$189.00 list price