A flow-equalizing device that is fitted to tube breathing apparatus. There are two kinds in general use, one consisting of a flexible, corrugated rubber tube and the other a canvas fabric bag. On inspiration, air is drawn partly from the equalizer, which is reduced in volume, and partly from the tube. On expiration, the equalizer restores itself to its original volume and in doing so draws air through the tube. Thus the air is kept flowing very nearly in a continuous stream, and the wearer, without the aid of bellows or rotary blower, experiences very little resistance to breathing.