The Patented Superior AccuTrak® VPE Ultrasonic Leak Detector is a cutting-edge, non-invasive ultrasonic leak detector that can detect both pressure and vacuum leaks of ANY GAS. The AccuTrak® VPE is perfect for locating leaks in air conditioning, refrigeration,automotive, and other systems. AccuTrak® Ultrasonic Leak Detectors respond extraordinarily well to the ultrasonic sound of a turbulent gas leak. They use a process known as "heterodyning" to transfer ultrasound to a lower frequency that your ear can understand. AccuTrak® Ultrasonic Leak Detectors keep the ultrasound's original acoustic properties, allowing leaks to be distinguished from competing background sounds. AccuTrak® Instruments are so sensitive that you can hear a blink of an eye, although most background noise does not affect with detection accuracy.