我想問正常人在幾多呎高空可以跳降傘

A typical jump involves individuals jumping out of aircraft (usually an airplane, but sometimes a helicopter or even the gondola of a balloon), travelling at approximately 4000 metres (around 13,000 feet) altitude, and free-falling for a period of time before activating a parachute to slow the landing down to safe speeds.
http://en.wikipedia.org/wiki/Parachuting
i.e. 4000 米 (~13,000呎)

2000-1500呎