Abstract: A treatment device is attached to a sealed container to provide clean replacement atmosphere to maintain the purity and cleanliness of the uncontaminated liquid remaining in the container. The device includes a valving system arranged to control flow of atmosphere into and out of the container, and includes a bubbler filled with treatment liquid, such as a disinfectant or purifying agent. Filtered air is bubbled through the treatment liquid prior to feeding the replacement atmosphere into the sealed container. In one embodiment, a floating valve assists in preventing undesired suction of the treatment liquid into the container. In another embodiment, the treatment device is attached to exhaust atmosphere to keep an ambient area clean as new liquid is added to the container and harmful atmosphere is exhausted. Methods related to the above are also defined and claimed.