If it were a true emergency and you had no other way out and you happened to be carrying a full leg air splint, then you might be able to wrap the foot in something that would keep it from shredding and walk on it if the injury wasn't too bad. Obviously, I don't think anyone would recommend it. You'd be far better off making yourself an impromptu crutch or crutches.

As for the mask, one of the more experienced folks will chime in, I'm sure. But for a First Responder you would probably carry either a collapsible mask or a folding plastic sheet with a barrier. The folding plastic ones are very compact and when stored correctly they seem durable. Don't get the cheap ones as the filter will separate from the plastic protector. Even so, I don't think they offer the protection or the utility of a collapsible face mask. That's protection for YOU, not for the victim. Most adult sized masks aren't going to work for very young children or infants. I'm just a first responder, so these things generally stay in your bag at my level. Paramedic Pete probably carries both sizes on his belt in a sturdy container.