>>1436154>that gigantic dead volumeA closed-face respirator needs a tight fitting cup over the nose and mouth. This forces exhaled air out, preventing it from mixing with the fresh filtered air. It also helps keep the visor from fogging. OP also does not seem to have any cartridges; are they concealed inside the helmet part or something? Careful design might let the filter media double as kinetic energy absorbing liner as well, a real synergy! The helmet / gas mask combo idea does have some potential, both for cycling and elsewhere.
