Homemade gas mask/respirator blower system

Homemade gas mask/respirator filter blower system that uses 40mm NATO filters to pump clean air into a respirator. The pump unit is designed to inflate camping beds etc, but can be modified with a little effort to work fine with respirators.
The hose used is a 40mm GOST hose, as with a positive pressure system this will make a safe seal with both GOST and NATO masks.