VX is a very persistant chemical, and readily combines with wood, cement, and other readily encountered building materials. It also volatilizes readily, but in a metered manner (it will constantly vaporize to remain an inhalation hazard) What this means is, once an area is contaminated, it is deadly for a LONG time.
Several tons of VX remain in the US arsenal however. There was an emergency at the Bluegrass army armory in Kentucky a couple of weeks ago, where a
155mm shell containing VX started leaking (was contained within its storage bunker).... However, if the bunker had been compromised, they would likely
have evacuated large parts of, if not all of Lexington KY.