Abstract: An emergency breathing device for use in a toxic environment including a clear plastic hood having sealing means about the neck or body to form a generally airtight enclosure about the wearer's head. A canister containing carbon dioxide and water vapor adsorbent material is mounted on a mouthpiece which is located completely within the hood. The mouthpiece directs inhaled air directly into the mouth and directs exhaled air through the adsorbent material before discharging it into the hood interior. An oxygen enriched carbon molecular sieve may be located within the canister whereby oxygen molecules trapped within the sieve are replaced by the carbon dioxide and/or water vapor and are liberated into the hood to enrich the oxygen concentration thereof to extend the breathing time of the wearer.