Airplanes with HEPA filters are the safest place to be though
...but that cough from the guy right next to me didn't go through the HEPA filters.
Reminds me when USPS put in filters after the anthrax incident. They installed them right above the operators on the DBCS's (their main mail sorting machines). The feeder was right in front of the operator. Mail was feed 35k pieces/hr by rubber belts. Small particles of paper dust are generated by the friction. The filter would draw the dust up in the air right pass the operators mouth and nose. You can't make this stuff up.