exposures to vacuum. There is only a limited amount of data available from human accidents, but it is consistent with animal data. Limbs may be exposed for much longer if breathing is not impaired. Robert Boyle was the first to show in 1660 that vacuum is lethal to small animals. An experiment indicates that plants are able to survive in a low pressure environment (1.5 kPa) for about 30 minutes. Cold or oxygen-rich atmospheres can sustain life at pressures much lower than atmospheric, as long as the density of oxygen is similar to that of standard sea-level atmosphere. The colder air temperatures found at altitudes of up to 3 km generally compensate for the lower pressures there. Above this altitude, oxygen enrichment is necessary to prevent altitude sickness in humans that did not undergo prior acclimatization, and spacesuits are necessary to prevent ebullism above 19 km. Most spacesuits use only 20 kPa (150 Torr) of pure oxygen. This pressure is high enough to prevent ebullism, but decompression sickness and gas embolisms can still occur if decompression rates are not managed. Rapid decompression can be much more dangerous than vacuum exposure itself. Even if the victim does not hold his or her breath, venting through the windpipe may be too slow to prevent the fatal rupture of the delicate alveoli of the lungs. Eardrums and sinuses may be ruptured by rapid decompression, soft tissues may bruise and seep blood, and the stress of shock will accelerate oxygen consumption leading to hypoxia. Injuries caused by rapid decompression are called barotrauma. A pressure drop of 13 kPa (100 Torr), which produces no symptoms if it is gradual, may be fatal if it occurs suddenly. Some extremophile microorganisms, such as tardigrades, can survive vacuum conditions for periods of days or weeks. Examples See also Decay of the vacuum (Pair production) Engine vacuum False vacuum Helium mass spectrometer – technical instrumentation to detect a vacuum leak Joining materials Pneumatic tube – transport system using vacuum or pressure to move containers in tubes Rarefaction – reduction of a medium's density Suction – creation of a partial vacuum Theta vacuum – vacuum state of semi-classical pure-Yang Mills theories Vacuum cementing – natural process of solidifying homogeneous "dust" in vacuum Vacuum column – controlling loose magnetic tape in early computer data recording tape drives Vacuum deposition – process of depositing atoms and molecules in a sub-atmospheric pressure environment