Modeling explosion in PHAST 6.54

[safetyuser]

"the building volume of the compresssor station"
how i can calculate
1/ confined volume
2/flammable mass in the cloud

Well, I don't know exactly your problem anyway from your few words I can suppose:
1- confinement is 100% if your compressor is totally enclosed in a building/box-shaped shelter and similar
2- the flammable volume in the cloud may be estimated in the worst case as the Upper Flammable Limit (UFL) of the congested gas, times the total confined volume. Use the gas density to turn into mass.

[Dushmen]

2- the flammable volume in the cloud may be estimated in the worst case as the Upper Flammable Limit (UFL) of the congested gas, times the total confined volume. Use the gas density to turn into mass.

It would be more correctly to use the difference between UFL and LFL.

[hamidkeng]

It would be more correctly to use the difference between UFL and LFL.

Why difference? Did you mean average?