The EV9520 Smoke Pro from Mac Tools functions by puffing smoke into one of a car's sealed systems, which produces tell-tale wisps of smoke and pinpoints the location of the leak. After the leak is repaired, the mechanic uses the Smoke Pro's pressure gauge to perform a decay test to confirm that the system holds pressure, scientifically ensuring that the system is properly sealed. The SmokePro can do much more than detect vacuum leaks. It can be also be used to detect oil leaks, exhaust leaks and transmission leaks.