[fingerlocks]

Sounds like you need to change your cabin filter.

[dnemmers]

I think the 'make bad air' part, is that it allows carbon dioxide levels to build up...not that the air is unpleasant to the senses to breathe.

[josephg]

Perhaps a lot of people should change their cabin filters.

Air quality should be good everywhere. But its not. You can't tell if you don't measure it.