After doing a bit of research, I narrowed it down to two options: Airthings View Plus [1] and Awair Element [2], both around the £300 mark which is acceptable in terms of budget.
Is there anything better in that price range? I don’t mind going a bit higher if required.
Thanks in advance.
[1] https://www.airthings.com/en-gb/view-plus
[2] https://uk.getawair.com/products/element
https://www.airgradient.com/open-airgradient/instructions/di...
... and some changes will also take some time to show effect. For me it was the amount of radon in the air.
Though usually those only detect particulate matter since air purifiers don't really help with CO2, etc.
That aside, I LOVED the Awair. There's a great story by DHH online on how his entire family got into somewhat serious health trouble due to heavy VOC exposure, and the Awair basically revealed all of it (I think it was an interview on YouTube).
Just be aware that the cheaper devices use cheap sensors to estimate certain measurements and aren't as reliable. There's some on Ali Express you can buy and wire up yourself (or use HomeAssistant with it). I prefered the Awair due to its neat look.