Bubble flowmeter is a simple and precise way to measure flow rates of gases. It determines the volumetric flow rate by measuring the time taken by the gas stream to move a soap bubble through a specific volume. Bubble flowmeters can be suitable to check splitter or detector flow or to calibrate personal pumps for accurate air sampling.

The most basic configuration of a bubble flowmeter is a calibrated tube, a stopwatch, and a good eye. The bubble is timed as it moves up the calibrated tube between two markings. A alternative tubing attachment port at the top of the flow tube allows the measurement of negative displacement. Flow tubes are graduated as follows:

• 500 mL tube in 50 mL increments
• 1000 mL tube in 100 mL increments

Includes the glass flow tube, 30 in. (3/4 m) of 5/16 in. Tygon tubing, a squeeze bulb, a collapsible stand, and a bottle of liquid soap solution.

Bubble flowmeter may be used to manually control the flow at the system outlet during analysis of perfluorobutane (PFB) in the exhaled rat air using respiration-metabolism chamber system and a GC-MS method.