Veterinarians commonly encounter low-oxygen environments in enclosed spaces that contain biologically respiring materials. Freshly cut plant material will continue to be metabolically active, and thus potentially consume oxygen from the air, for surprisingly long periods of time. If such materials (eg, grains, hays, freshly cut timber, etc) are stored in sealed confined spaces (eg, silos, ship holds, etc) with little ventilation, a low-oxygen atmosphere will develop. Such circumstances have resulted in significant human casualties and deaths. Such environments should always be treated with suspicion, and their atmosphere tested for the presence of breathable air; testing with a flame is not an adequate method. It is strongly recommended that individuals do not work alone in such environments and that a method of safe extraction of a person entering into such environments is immediately available.
Entry into low-oxygen environments can result in rapid loss of consciousness and death. Typical signs and symptoms of hypoxia include lightheadedness, fatigue, numbness, tingling of extremities, nausea, ataxia, confusion, disorientation, hallucinations, behavioral change, severe headaches, reduced consciousness, papilledema, breathlessness, pallor, tachycardia, and tachypnea, with eventual progression to cyanosis, slow heart rate/cor pulmonale and low blood pressure, and death.
Ill-considered and poorly equipped rescue attempts from low-oxygen environments have resulted in many human casualties. Rescue operations under such circumstances are best performed by properly equipped and trained professionals.