Bruce Gordon BLT, Cannondale parts bike, Ecodyne recumbent trike, Counterpoint Opus 2, miyata 1000
Trog, I used to specialize in underground mine ventilation for the Federal Mine Inspectors. As nasty, wet, dirty, hot and cold a place as you can imagine. I found that people doing heavy exercise had severe problems getting enough air thru filters powered by their own lungs. We even tried hard hats with powered fans and filters built into the hat, blowing air, contained by a full face shield, down across the face. That worked with a problem of the face shield fogging over. The test was made in the Skyline coal mine near Aspen, Colorado. A cyclist might have problems with the five pound battery pack miners carried on their belts to power the fan for a ten hour shift. An alternate system was rigged by a cycling friend who worked in a Denver hospital. He had severe allergies. He had a battery-powered filtering system on his rear rack. That fed a respirator hose leading to a face mask. On a ride in seemingly crystal clean air in the mountains he still wore a basic dust filter over his nose and mouth.
Try a safety supply store near where you ride. Explain what you want to do and see what they suggest.
If that does not work try someone in the medical field. Ken