I tested it on r22, and r410a and it seemed to work good, I did have to have the sensitivity all the way up but sometimes that's better so you don't get false readings,
I have used this tool in addition to using dye in my AC system.. I have worked on a couple vehicles where visual inspection is not quite as easy as quick use of this tool. I found it very helpful. Good bargain for the money.
works great, used to find leak on tractor a/c. found leak within minutes that l could not find before. only problem was battery compartment door does not close good.
This is comparable in sensitivity to the $200 halogen leak detector I used as a technician many years ago, yet only a quarter of the size and a tenth the price.
great for the price