that's what they said many years ago about the problems of the exhaust gases and particulates - 'the wrong size to cause health issues' they said - it's the same particulates that are being blamed fro inner city pollution and poor air quailty.....
Having the heating on for extended periods always left me feeling flush-faced and with a slight headache - classic symptoms of mild CO poisoning - some of the air came from around the combustion chamber ISTR.
And one reason why North Sea cabs had to have a ten minute dry run before flying with pax due to the risk of poisoning them, pilots and engineers were a different species apparently.
SND