Medical/surgical personal protection system including a fastening system for holding the hood to the helmet so the radius of curvature of the hood face shield varies

A head unit (270) for a personal protection system and configured for use with a hood (92) that includes a transparent, flexible face shield (590) is described. The head unit includes a support structure (272, 286, 428, 430) for supporting the hood (92) around the head of a wearer, a fan (433) attached to the support structure for drawing air through the hood, and mounting means (296, 524) integral with the support structure (272, 286, 428, 430). The mounting means (296, 524) engage complementary hood face shield mounting means (594, 596) for removably securing the hood (92) over the head unit so that the face shield (590) is located forward of the face of the wearer and is curved around the face of the wearer. Further, the mounting means (296, 524) are arranged so that, when the support structure mounting means engage the face shield mounting means (594, 596), the radius of curvature of the face shield (590) varies along a top to bottom longitudinal axis of the face shield such that a top section of the face shield has a first radius of curvature and a bottom section of the face shield has a second radius of curvature smaller than the first radius of curvature.