placement of k.o. drum

Can we place K.O. drum in a pit with in gas plant especially when the gases are heavier than air? If the answer is yes, is their any reference available in any international code (especially in American or BS code) that we can use for detail study and onward working?

 

[01101998]

the heavier gases would not disperse fast in case of leakage if they accumulate in pit. If your gas is LNG or LPG this can be dangerous. But underground lpG bullets are common so I hope codes don't prohibit that.
Just my views ,nothing sure: