General Tools RLD400Digital Refrigerant Leak Detector with Pump.

The modern, electronic way to maintain mobile and stationary air conditioners, refrigerators, chillers and heat pumps. New proprietary semiconductor sensor detects many new ozone layer-friendly refrigerants approved under the U.S. EPA's Significant New Alternatives Policy (SNAP).
 
Why look for refrigerant leaks? There are three reasons to detect and repair leaks of refrigerant gasses from stationary and mobile air conditioners, refrigeration systems and heat pumps:

1. Leaks allow air and moisture to enter an A/C system or chiller. Moisture can react with refrigerant to form corrosive acids and sludge that can damage a compressor, plug up orifice tubes, and/or eat pinholes in evaporators and condensers.
2. Refrigerant is expensive. It may seem cheaper to keep recharging your system with refrigerant than fix a leak, but it isn't in the long run. Also, A/C systems and chillers that arent fully charged won't cool efficiently and thus waste money (electricity-powered systems) or fuel (vehicle systems).
3. Most refrigerants deplete the ozone layer that blocks the sun's harmful ultraviolet radiation. In the U.S., the Clean Air Act of 1990 and later amendments require owners or operators of refrigeration and air-conditioning equipment with refrigerant charges greater than 50 pounds to repair leaks within 30 days when those leaks result in the loss of more than 15% (comfort cooling) or 35% (commercial cooling) of the charge over a 12-month period.