Deadspace (in breathing apparatus)

Deadspace in a breathing apparatus is excess space which the flow of air or breathing gas must pass through and back again as the user breathes in and out, increasing the necessary respiratory effort to get the same amount of usable air or breathing gas, and risking accumulation of carbon dioxide from shallow breaths. It can be reduced by:

• Using separate intake and exhaust passages with one-way valves placed in the mouthpiece.
• With a fullface mask:
  • Keeping its inside volume small.
  • Having a small internal orinasal mask inside the main mask.

A smaller space around the mouth increases the "gasmaskyness" distortion of speech.