NEW – Sonoff Airguard PM3.5 and Airguard CO2

Released on December 11, 2025, these two new identical-looking products run on USB power (each comes with a 2m USB-A to USB-C lead). On opening the package, I thought at first that Sonoff had sent me two of the same product. It took me a few seconds to realise the displays were slightly different.

No, your eyes are not deceiving you. Above are two completely different products with the only give-away being the details on the back – below.

Time for a quick test…. out of the box I put each of the two units one at a time on my desk – and the difference becomes obvious immediately. Both show temperature and humidity at the bottom of the screen, while the O7P is showing particles in the air – PM2.5 output showing here at 50 microgram per metre cubed. On the other hand, the O8P shows CO2 levels just under a thousand ppm.

Bear in mind that I’ve not yet connected these up to anything – just provided USB-C power and turned them on. I’ve not even given them time to settle. As you see the displays (not backlit) are clear and bright in office lighting – just like the Switchbot unit.

Both have a little loudspeaker symbol showing that sound is available (alarms). In fact, the first unit blasted an alarm at me when I first turned it on, so I disconnected it. I tried the second unit, and later went back and tried again. No alarm this time – the air in here is perfectly normal given that I’m in my office just outside of town in a rural area in Southern Spain.

How do I know these levels are near normal? Because I’ve tested several similar units from other manufacturers including the Switchbot Meter Pro unit you see below and my Apollo Air-1 unit which combines various gas sensors and particle sensing in one unit..

Now before anyone gets excited, the 3d-printed Apollo Air-1 unit while being FANTASTIC and comprehensive – has no display and is designed specifically for Home Assistant – relying on Home Assistant to provide a shed-load of useful information. It also costs (American dollars from $99 to $199 – the latter with the CO2 sensor). I reviewed the Air-1 back in February 2025 and urge enthusiasts to go have a look.

Meanwhile, we have the Switchbot Meter Pro unit which has a landscape format and is as much at home in the living room as the Sonoff devices.

I LIKE the Switchbot Meter Pro (CO2 monitor), it runs on batteries and I’ll take this opportunity to rectify the fact that I never actually reviewed it. As you can see above: time, date (I must fix that USA-format date) – it reports back to Home Assistant, tells you WHEN it last took a CO2 reading and again shows temperature and humidity. The cost is something in the order of 80 Euros.

The Meter Pro when hooked into Home Assistant reports battery level, CO2 level, temperature and humidity – that’s it. Basic compared to the Apollo unit, but like the Sonoff devices in this article, looks absolutely at home in the living room – and I have to tell you has been running now for over a year on a (supplied) pair of quality AA batteries – as you can see the batteries are still at around 50%. Despite not apparently writing about the unit, I have a trail of emails from Switchbot as the Meter Pro initially would not connect to Home Assistant (historical – it’s been fine for a long time).

SO – that out of the way, let’s get back to the Sonoff SAWF-07P and 08P which, in common with other Sonoff devices are well made and compatitively priced at around 39 euros/dollars for the CO2 unit and 49 euros/dollars for the particle sensing SAWF-07P unit on the Sonoff website – in this case pricing is WAY, WAY below either of the two units discussed above. Im not sure since when dollars and euros became interchangeable 1 to 1.

I’m currently running the Sonoff CO2 unit and Switchbox CO2 unit on my desk next to each other and there seems to be a discrepancy – Switchbot says 650ppm, Sonoff says 952ppm. I’ll leave them running for a while as I head off to the local wine festival. Several hours later, Switchbot 403ppm, Sonoff SAWF-08P 698ppm.

Ok, got a problem – Apollo Air-1 unit – the most expensive of the lot – same room, same conditions – just a couple of metres away says CO2 602ppm.

And while I await to hear from the various companies – I’ll connect the Sonoff CO2 unit to the eWeLink APP. It can connect to Matter but the rest of my Sonoff WiFi devices connect via the Sonoff integration in Home Assistant so this is the best route for me.

Connection to the eWeLink APP complete – showing temperature, humidity, CO2 level. However – going further – connection to Home Assistant – I’m seeing nothing but an elapsed time sensor.

In the end I only had the one CO2 unit from Sonoff – and I asked both Sonoff and Switchbot for a second unit to compare. I received second one from Switchbot. I tested all three outside, next to each other and after waiting an hour or so to let them settle (and carefully avoiding breathing on them), CO2 levels still varied wildly. I’ll leave you to draw your own conclusions until I get a second CO2 device from Sonoff.