Nimbus One reads particulates, carbon dioxide, volatile organics, temperature and humidity every ten seconds — on the device itself, and in an app that keeps thirty days of history.
A real reading from a two-bedroom flat in Bristol, 2 August 2026, taken forty minutes after cooking.
One number on the device answers whether to open a window. Thirty days of them answers why the back bedroom is always stuffy by morning — and whether the extractor fan is doing anything at all.
Every reading at ten-second resolution, stored on the phone. Export the lot as CSV whenever you want it.
A notification when carbon dioxide passes a number you choose — not a number we chose for you.
The app polls the device over your own network. An account is optional, and only needed if you want readings from somewhere else.
Ranges and tolerances below are the figures we test to, not the best case from a supplier datasheet.
Frying, toasting, candles, a wood burner, pollen and road dust. PM2.5 is the fraction small enough to pass the lungs and enter the blood, which is why it is the number most air-quality guidance is written around.
A proxy for how much of the air in the room you have already breathed. Outdoors sits near 420 ppm. A closed bedroom with two people in it reaches 2,000 ppm by morning, and most people report feeling dull somewhere above 1,000.
Solvents off cleaning products, fresh paint, new furniture and printer toner. Reported as a relative index rather than a concentration, because a low-cost sensor cannot honestly tell you which compound it found.
Below 40% relative humidity you get static, dust and dry throats. Above 60% for any length of time you get mould in the cold corners. The sensor sits away from the board so its own heat does not skew the reading.
The short version. Sensors, connectivity, power, physical and compliance are all on the device page.
Full specification →model NB-1
Nimbus One is a sensor, so it reports into whichever system you already use rather than asking for another app on the home screen.
Appears as four HomeKit sensors. Automations evaluate on your own hub, so nothing leaves the house.
Certified as a Matter 1.3 air-quality sensor. Pairs with any Matter controller using the code on the base.
Ask a speaker for the current reading, or start a routine when a threshold is crossed.
Announcements on an Echo — useful for carbon dioxide, which you cannot smell or feel coming.
Local polling over the LAN, discovered automatically. No cloud account, no API key, no rate limit.
An unauthenticated read-only endpoint on the local network, documented on the support page. Turn it off in settings if you would rather it were not there.
It sits on a shelf and gets on with it. No screen to wake, no app to open, no subscription to forget to cancel.
“Across seven days of side-by-side logging against our reference NDIR meter, the Nimbus tracked to within 60 ppm. Two of the five monitors in this test drifted by more than 300.”
Tom RowleySensor Review · 12 May 2026
“I unplugged the router and kept testing. It was the only monitor here whose app still showed live readings and still fired its alerts.”
Priya NandakumarThe Quiet Home · 3 June 2026
£149 including VAT. We do not sell direct — the directory lists the official store and every authorised retailer, with who ships where and who handles warranty service locally.