An altitude simulation assembly for an environmental chamber includes: at least one ambient air inlet； an air compressor downstream of said ambient air inlet for compressing the ambient air； at least one gas separation means downstream of the air compressor for separating the compressed air into hypoxic gas and hyperoxic gas； and, at least one fluid flow control means in fluid communication with the at least one gas separation means, for controlling the flow of hypoxic gas and hyperoxic gas to the environmental chamber. The at least one fluid flow control means is in fluid communication with at least one outlet port for supplying hypoxic gas from the gas separation means to the at least one outlet port, and hyperoxic gas from the gas separation means to the at least one outlet port. The fluid flow control means controls the oxygen concentration of gas to the environmental chamber.
