[*BCM*] Filter Masks

[Ben Hunrichs]

As I understand it, any surgical mask you're likely to want to wear 
while riding a bike won't do anything to filter out car exhaust.  Cloth 
surgical masks are there to prevent particles of spit from getting on 
the patient.  To protect yourself from small particles (including most 
bacteria), you'd need to have a mask that sealed very well on your face 
and had built in filters (HEPA filters for biological contaminants).  
This type of mask may help with some of the particulate matter in car 
exhaust, but are unlikely to do anything at all for the gaseous 
components.  For that you need a separate air supply or some kind of 
elaborate filtering mechanism (maybe activated carbon, I don't know).

I've used HEPA filter masks and they're no fun to wear.  They get sweaty 
and you have to exert extra effort to force your incoming air through 
the filters.

ben