[labnetwork] Help ... Please !!! ... our safety guys have not clue about gas cabinets ...

[John Shott]

Leo et al:

Just to add another point of reference to this discussion.

Normally, our bottles are open and charged with gas all of the time ... 
50 weeks a year around the clock.  Gas detectors, seismic switch, etc 
shut the pneumatic valve in the pigtail in the event of a problem.

We do valve off the bottles during the holiday shutdown with product 
still in the lines ... but not for the safety reasons that you imply.  
During this shutdown period, we have 100% sensor testing with live gas 
performed by a third party with county hazardous materials inspectors 
witnessing each test.  That normally takes two full days and often has 
the TGO system in a state where it wouldn't call the fire department, 
for example, in the event of a real emergency.  Also, during that time, 
our fume scrubbers are shutdown for annual cleans.  When they are 
shutdown we have no ability to treat for a catastrophic leak so having 
the bottle valves shut eliminates the chance of a big release.  Finally, 
with the bottle valves off, it also allows us to check for static creep 
in the regulator and, by watching for high- or low-pressure changes over 
a period of days, provides at least a modest double-check of any leaks 
in the system.  In other words, because we are not using any of the 
gases and because we are working on systems that support those gases in 
various ways, we shut the bottle valves but without purging the gas lines.

Thanks,

John