Introduction The DU-III Blast & Gastight Door is a protective shelter door designed to withstand blast pressure exceeding 440 kPa (4.4 bar) and provide gas tightness. According to the product information published by Atmas Group, DU-III doors are designed for civil defence shelters and other protected facilities. They are available in single-leaf and double-leaf configurations. Atmas Group The door leaf is constructed from reinforced beams with steel cover panels. The design