Compressed air is used in many machines. Air drills are widely used in mining and in various types of construction work. Compressed-air drills and hammers are used for breaking concrete sidewalks and pavement when it is necessary to remove them. The iron rivets which hold together the bodies of steel vessels and the steel frames of buildings are driven and fastened with compressed-air machines.
Compressed air, when released as an air jet, is used in such devices as the barber’s hair-drying machine, the hand-drying machine, and the “paint gun.” The sandblast consists of an air jet which carries sand. It is used in smoothing cast-iron surfaces and in cleaning the outside walls of stone or cement buildings.
In the use of air brakes on streetcars and railroad trains, compressed air forces the brakes against the wheels. The familiar shrill whistling sound that follows the use of air brakes is caused by the escape of the compressed air when the brakes are released. Door checks, life belts, pillows, cushions, and many other devices may be listed among the articles in which compressed air is used. The air rifle is also a good illustration of the use of compressed air.