I agree that the little mouth shields with the one-way valve that you carry on a key chain are not the best choice. Had opportunity to use the "keychain" style once and it was a pain, but better than nothing, That's why I keep a large faceshield with one-way valve and oxygen port (hard shell case) in my backpack. The "keychain" style is just as a last resort.

Just a thought about EDC infection control; not a bad idea to keep a pair or two of medical exam gloves on you, or handy just in case you feel the urge to stop and help out on a wreck, deliver a baby, etc... I keep two pair in my fanny pack and they don't take up much room. Plus, they came in handy when I had to do a little parking lot repair job on my car (kept my hands from getting dirty)

peace,
samhain