Apparatus is described for storing sensitive materials in containers (32) which are sealed and in which the internal atmosphere may be purged by flushing with an inert gas fed in from a purger unit (30) via a suitable feed lead (35). The gas exhausted from inside the container (32) is fed back into the purge unit (30) and then checked against a desired parameter, for example oxygen concentration, until the value of that parameter reaches a desired level. Purging may then be stopped and the container left sealed, preferably at a slight over pressure relative to the ambient atmosphere. The use of a separate purge unit enables many containers to be sequentially and effectively processed. The containers are particularly useful for storing sensitive chemical and biological samples.