Gas Tight Suit : Generally considered same as "Level A" suit or "vapor protective suit". Term may be misleading in that no suit is 100% gas tight, there is a 20% pressure drop allowed by the ASTM F1052 pressure test standard
DuPont (The Miracles of Science), Literature & Technical Information, Industrial Personal Protection Glossary, Wilmington, DE, USA 2010http://www2.dupont.com/Personal_Protection/en_ HK/tech_info/glossary_industrial.html, (IndPP - Amer) {49}