Aranet4 Home Wireless Indoor CO2 & Air Quality Monitor review
Knowing, from the other side of the room and without touching your phone, when to open a window.
By Tom Calder · Updated 24 July 2026 · Price checked against our tracker
The best CO2 instrument in this cluster by a clear margin, with a manufacturer-stated NDIR accuracy of ±(30 ppm + 3% of reading) and a display you can genuinely read across a room. It does one job properly and makes no pretence otherwise: no particulates, no VOCs, no radon and — this is the point readers most often get wrong — no carbon monoxide whatsoever. Bluetooth only, so there is no checking in on it while you are out.
UK prices sit in a spread rather than at one figure: £139.00 at duomo.co.uk bundled with a wall bracket, £159.00 at GMCiUK, and roughly £169–£175 reported on Amazon.co.uk as of 24 July 2026. We list the middle of that range. Some UK retailers sell it as the "SAF Aranet4" — SAF Tehnika is the manufacturer, so that is the same product, not a clone.
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- Manufacturer-stated CO2 accuracy of ±(30 ppm + 3% of reading) from an NDIR sensor
- Large-digit e-ink display with traffic-light status, readable from across a room
- 2x AA lasts years — up to around four on alkalines, up to seven on lithium cells
- CO2, temperature, humidity and pressure only — no PM2.5, VOC, radon or carbon monoxide
- Bluetooth only with no Wi-Fi, so no remote checking or alerts when you are out of range
- That accuracy figure is a manufacturer specification, not an independently certified one
Key specs
| Measures | CO2 (NDIR), temp, humidity, pressure. No PM2.5, VOC, radon or CO. |
| Display | Large-digit e-ink, readable across a room, traffic-light status |
| Connectivity | Bluetooth only — no Wi-Fi; Aranet Home app for history/export |
| Power | 2x AA — up to ~4 years alkaline, up to 7 years on lithium |
Our rating is a considered spec-and-evidence verdict: we verify every specification against at least two independent sources, track the UK price daily, and say plainly who a product isn't for. Commissions never change a rating. Read the full methodology →
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