Abstract: A safety breathing apparatus has a delivery element configured to deliver respirable gas to a respiratory system of a user. The apparatus includes a breathing hose in fluid communication with a first source of respirable gas. A valve housing includes a first port configured to be couple to the delivery element, a second port configured to be coupled to the breaking hose, and a third port configured to dock with a second source of respirable gas without exposing the user to a surrounding atmosphere.

Abstract: Described herein is an adapter having a housing defining an internal passageway, a first connecting end portion having a first opening to the internal passageway, a second connecting end portion having a second opening into the internal passageway, and an exhalation valve disposed on the housing. The first connecting end portion is configured to mechanically and fluidically couple with a lung demand valve. The second connecting end portion is configured to mechanically and fluidically couple with a mask of a closed circuit breathing apparatus. Related apparatus, systems, and/or methods of use are also described.