The time limit for. shipping a POV is the same as for travel and HHG transportation limits (JTR Para 5366, POV. Transportation Time Limitation), 1 year from the date of retirement/separation with severance. pay or 180 days from the date of separation.
The envelope is the large bag that holds the helium gas. The envelope is generally cigar-shaped, for aerodynamic purposes, and made of a durable, airtight, lightweight fabric (polyester composites) that is much like the fabric of a space suit.
Helium is commercially recovered from natural gas deposits, mostly from Texas, Oklahoma and Kansas. Helium gas is used to inflate blimps, scientific balloons and party balloons. It is used as an inert shield for arc welding, to pressurize the fuel tanks of liquid fueled rockets and in supersonic windtunnels.