Sundstrom SR500 powered air purifying respirator are the safest way to filter the air.

Twin filters filter more air, for longer, and battery-powered fans push the clean air to your facemask (not included). 

The fan can be used with Sundstrom hoods, face shields or full face masks (mask & hose not included). 
The fan unit must be fitted with a pair of suitable filters(filters not included).