CO2 levels are shown at, for example,
www.kane.co.uk. UK outdoor air is usually around 400ppm. 5,000ppm is a common maximum indoor workplace level maximum.
My experience is that I am used to around 300ppm (home office with an open window), probably because I live near mountains where the air is known to be good. At 600ppm (normal in a room where I am doing physical work) I can tell the difference, at 900 (sleeping alone with the window closed) I feel the room is a but muggy, at 1,200 overnight (two of us in the same room with the window closed) I wake up feeling groggy. Our CO2 meter's display goes from green to yellow at 1,000ppm and to red at 1,400ppm.
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As for PM2.5 and PM10, the government's web site says (
here):
The Air Quality Standards Regulations 2010 require that concentrations of PM in the UK must not exceed:
An annual average of 40 µg/m3 for PM10;
A 24-hour average of 50 µg/m3 more than 35 times in a single year for PM10;
An annual average of 25 µg/m3 for PM2.5.