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 an inert gas. The only gas with a lower reactivity is neon. This low reactivity makes helium a valuable gas to use in manufacturing and repair processes when an inert atmosphere is required. Helium also has the second lowest density of any gas along with a very high thermal conductivity.These properties of helium gas make it the atmosphere of choice for many metallurgical processes, growing perfect crystals in chemical vapors, manufacturing optical fibers and other uses.Helium has a very low viscosity, a high diffusion coefficient and the smallest atom of any element.hese properties of helium gas make it the atmosphere of choice for many metallurgical processes, growing perfect crystals in chemical vapors, manufacturing optical fibers and other uses. Helium has a very low viscosity, a high diffusion coefficient and the smallest atom of any element.