It is used for applications that do not require high sensitivity. With bubble testing, the part under test is pressurized, submerged in a liquid—typically water—while the operator looks for bubbles. Bubbles form at the source of the leak as a result of air pressure, and the number of bubbles per minute can signify the size of the leak.
If a more sensitive test is required, the “Pressure Change/Decay Method” can be applied. The pressure decay testing method measures the decrease in pressure in an object. A test object is initially inflated and then a reference pressure is established. After a designated amount of time, the pressure is monitored again, and the initial and final measurements are compared. The change in pressure can be used to calculate the leak rate given the internal volume of the device. Pressure decay is able to detect minute changes in pressure. A pressure drop signifies a leak; the greater the pressure drop, the larger the leak. This method is convenient in that it is easily automated and dry.