During a pre-trip daily inspection, how is a static pneumatic air leakage test performed on a commercial vehicle with the engine turned off?

1. By holding the horn down for 2 continuous minutes while revving the engine
2. With full system air pressure and engine off, release parking brakes, apply and hold the foot brake firmly for 1 minute, and verify that air pressure drop does not exceed the legal limit (~0.2 to 0.3 bar)
3. By disconnecting the main air line from the compressor while driving at 50 km/h
4. By smelling the exhaust tailpipe for escaping air