Eh, Data was plugged into something. Stands to reason that one of the cords was a power feed.

And it's a pretty common trope (tvtropes.org) in scifi to decompress an airlock or cargo bay in order to expel something (contaminants, explosives, villains, etc.). Some even go so far as to say people can survive in space for a few seconds via this method, in order to escape emergencies, etc.