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..
What is the Fastest Airplane in the World? The Lockheed SR-71, the fastest airplane in the world. Though not the world's absolute fastest aircraft, the Lockheed Martin F-22 Raptor can accelerate to and sustain supersonic speeds without the use of its afterburners. The Boeing 747 has a cruise speed of 550 miles per hour, which is actually faster than the top speed combat fighters could achieve in World War Two.