Rich wrote:
I understand Coby. I also had a personal interest here living this close
to a really congested road. I was kinda interested if any figures
existed and if anyone had more pointers for me. It's that my houses'
environmental system already has filters for dust but there's not any
consideration for CO/CO2 or SO/SO2 ..

cr*p .. and it only took me up to me getting into bed to realize I
actually wrote "S"O instead of "N"O .. sorry about the mixup!