REBREATHER APPARATUS

An apparatus for preparing a ventilation gas mixture to a user comprises: a gas mixing device configured to receive oxygen through a first gas feed, the gas mixing device being further configured to received exhaled air from a person; a gas reservoir configured to receive the exhaled air from the gas mixing device through a second gas feed, wherein the gas reservoir is further configured to re-supply the exhaled air to the gas mixing device through the second gas feed; an altitude sensor configured to determine altitude information; a control system configured to receive the altitude information from the altitude sensor and further configured to control the flow of oxygen through the first gas feed based on the received altitude information; wherein the gas mixing device is arranged to combine the oxygen received through the first gas feed with the re-supplied exhaled air received through the second gas feed in order to prepare a ventilation gas mixture.