IN the course of his employment by the Broken Hill Proprietary Co. the writer has had occasion to use and instruct others in the use of the Shamrock rescue apparatus. This short paper deals with the various types of apparatus tested. The common object of the various types of breathing apparatus is to enable the wearer to remain and work for varying periods of time in an atmosphere which is either deficient in oxygen or is poisonous - that is, contains carbon monoxide or irritating and irrespirable vapours, such as the smoke from underground fires, sulphur dioxide or ammonia fumes.