Abstract: The invention described herein relates to an apparatus for providing a selectively humidified gas to a camera canister (12) containing cameras and film used in space. A source of pressurized gas (leak test gas 26 or motive gas 21) is selected by a valve (30), regulated to a desired pressure by a regulator (34), and routed through an ejector (46) (venturi device). A regulated source of water vapor in the form of steam from a heated reservoir (18) is coupled to a low pressure region (50) of the ejector (46) which mixes with high velocity gas flow through the ejector (46). This mixture is sampled by a dew point sensor (14) to obtain dew point thereof (ratio of water vapor to gas) and the apparatus adjusted by varying gas pressure or water vapor to provide a mixture at a connector (78) having selected humidity content.