Abstract
This paper discusses current problems and new developments in the field of respiratory protective devices. Speaking diaphragms and electronic amplifiers have been introduced to improve voice transmission. In new designs, nose cups prevent fogging of the eye-piece lenses. Data on cold chamber tests are included. The reliability and acceptability of fit of the facepiece continue to be problems; fitting data from test results are presented here. New developments in combination supplied air and air purifying respirators are discussed.
