Yeah, confined spaces and compressed, flammable gases are not a good mix.
However...
If it's a closed but well ventilated space, the equation changes. You gotta have vents in, could be screened, louvered, etc. But you also need to have a floor that is vented, could be screened, holes, etc.
Thing is, those gases are heavier than air and will tend to pool in a closed space. Go to open, spark, BOOM!
But if the gases can't be confined by the space, then it's different. Not sure up to code or whatever, someone else may know more about that, but properly designed -- we're talking very well ventilated, not some puny 2" tube or something -- I'd think that should satisfy the usual concerns about this?