In the preamble to the final Respiratory Protection Standard, OSHA discussed extensively its rationale for requiring that employees breathe air consisting of at least 19.5 percent oxygen. The following excerpt, taken from the preamble, explains the basis for this requirement: Human beings must breathe oxygen . . . to survive, and begin to suffer adverse health effects when the oxygen level of their breathing air drops below [19.5 percent oxygen].
- The Tu-144 supersonic transport was the fastest commercial jet plane at Mach 2.35 (1,555 mph, 2,503 km/h). It went into service in 1975, but soon stopped flying. The Mach 2 Concorde aircraft entered service in 1976 and flew for 27 years..
It depends on the type of plane. Small, one-engine propeller planes (reciprocating engines) fly at speeds of 80 to 200 mph (130 to 320 km/hr). Jet airliners at cruising altitude average around 500 to 600 mph (800 to 960 km/hr). Military turboprops cruise at 350 mph (560 km/hr) and jet fighters routine exceed the speed of sound (768 mph or 1235 km/hr at sea level).