Definitely not when it is burning and creates lots of smoke. Coals should be partly grey and make less smoke.
The thing is that only persons who said they had good meter, used coals and got CO above 10 000-12 000ppm used coals a lot about 4.5kg.
But then there is discuss weion that some coals are much better. I wanted to test it since I have professional meter with bag of coals turned mostly grey (burned 1h-1.5h) in small space. But they created still lots of irritating smoke and CO levels rose slowly. Because of the smoke I decided to not test it any further, the CO level was 400ppm then.
In comparison I tested generator in small space and the air was normal (though smelled like gas station) above 3000ppm. It got to above 12000ppm every time fast and then started to slow down from lack of oxygen which is fine. That air is not fine to be long time in (no heat but smoky) but takes just one second.