VX is a rapid acting lethal nerve agent. It inactivates cholinesterase in tissue fluid similar to GB. It has a low vapor pressure; however, it can be absorbed through the respiratory tract as a vapor or an aerosol. Its primary hazard is absorption through the skin and eyes. It can also be absorbed through the gastrointestinal tract if ingested. VX evaporates slowly, and it may persist in the environment for several days. The vapor density is 9.2 compared with that of air. The permissible exposure limit (PEL) for an eight hour period is 0.00001 mg/m3. Exposure to a fatal dosage usually results in death in 15 minutes.