A leak detector will detect leaking fluids or gases. Since there are many different fluids and gases used in the industrial world, there are many types of leak detectors. Ultrasonic leak detectors are used for water and pipe leaks, vacuum and pressure leaks and exhaust system leaks. Infrared-based refrigerant leak detectors are used in HVAC applications. Helium leak detectors are used in the pharmaceutical, contract packaging and medical device industries to insure the integrity of the seals on packaging. Gas leak detectors can use helium or carbon dioxide to find leaks in welds, joints seams and gaskets that are under pressure.