Open Source Gas Mask
NOTE: This is a preliminary design, that still needs testing and refinement. Do not rely on this to save your life just yet.
This is a 3d printable gas mask design. It's printed in 3 parts - the main mask, the canister, and a gasket to hold the face shield in. The face shield is cut from a piece of clear plastic.
The filter material is activated charcoal - you can buy this at any pet store. Put a layer of cotton batting in the bottom of the canister, then fill with activated charcoal, then put another layer of cotton on top, and screw the canister into the mask.
Pull requests welcome!