An air gauge assembly is provided herein which allows for accurate comparative pressure measurements between SCBA's. Such precise measurements provide a highly accurate indication of air volume in an air tank of a SCBA; higher pressures mean more air, while lower pressures mean less air. The air gauge assembly includes a mounting member from which extends a pressure line terminating at an adjustable bleeder valve. The mounting member is formed to be mountable to air part of a SCBA. A pressure gauge is mounted along the pressure line which preferably includes a transducer and digital display. The pressure gauge is calibrated to provide a highly accurate reading of pressure in the pressure line. Advantageously, with the device of the subject invention, accurate pressure readings of single or multiple SCBA's may be obtained to not only monitor air volumes therein, but also to permit comparative testing. Such testing may include the testing of breathing techniques of different firefighters.