seal that goes around the wearer's neck that looks like a space suit helmet. They offer a good visual field. Light weight plastic hoses provide oxygen to the helmet and remove exhaled gas to the outside of the chamber. Oxygen helmets are often preferred for oxygen administration in hyperbaric oxygen chambers for children and patients that are uncomfortable wearing an oxygen mask. Mask retention systems Medical oxygen masks are held in place by medical personnel or the user by hand, or they may be fitted with a lightweight elastic headband so the mask can be removed quickly. Full-face masks are secured by several straps. Tightly fitting oxygen masks are secured at four points by two head straps. Aviators' masks are often equipped with "quick don" harnesses that allow those in pressurized aircraft to rapidly don the masks in emergencies. Military aviators' oxygen masks are secured to flight helmets with quick-release systems. See also References Dosage forms Drug delivery devices Medical masks Oxygen Safety equipment Respiratory therapy Ambulances Armenian inventions ja:マスク#その他のマスク