Oxygen systems are required on aircrafts that fly for extended periods at altitudes substantially above 10,000 ft.Although the normal human body can survive without a special supply of oxygen at altitudes of over 15000 ft, the mental and physical capacities of a human being are reduced when the usual supply of oxygen is not available in the air.It is particularly important that the pilot and crew of an aircraft have an adequate supply of oxygen when operating an unpressurized aircraft at altitudes in excess of 10000 ft.A lack of oxygen causes a person to experience a condition called hypoxia.This condition results in light-headedness, headaches, dizziness, nausea, unconsciousness, death depending upon its duration and degree.When permanent physical damage results from lack of oxygen, the condition is defined as anoxia.The importance of oxygen, especially when flying at higher altitudes, is not appreciated by many persons who fly, including pilots.It is generally known that the human body requires oxygen to sustain life, but the effects of a lack of sufficient oxygen on various functions of the body are not understood by many persons.TYPES OF OXYGEN SYSTEMS:Oxygen systems classified according to source of oxygen supply may be described as1. Chemical or solid state. 2. Stored gas.3. Liquid oxygen (LOX) systems.For private and commercial aircraft or of stored gas or chemical type.LOX systems are limited to military aircrafts.Oxygen systems may also be portable and fixed.The fixed system is permanently installed in airplane where a need of oxygen exists at any time during flight at high altitudes.Commercial airplanes are always equipped with fixed systems, augmented by a few portable units for crewmembers, who must be mobile and for emergency situationsOxygen systems are also classified according to the type of regulator that controls the flow of oxygen.CONTINUOUS FLOW TYPE:Majority of oxygen systems are of this type the regulator on the oxygen supply provides the continuous flow of oxygen to the mask. the mask valving provides for mixing of ambient air with the oxygen during breathing process.DEMAND & DILUTE REGULATORS:These regulators are used with demand mask and supply oxygen-using inhalation when the individual inhales; it causes a pressure reduction in a chamber with regulator. This reduction in pressure activates oxygen valve and supplies oxygen to the mask. The demand mask covers most of users face and creates an airtight seal. This why a low pressure is created when the user inhales.PRESSURE DEMAND REGULATOR:Such regulator contains an aneroid mechanism, which automatically increases the flow of oxygen into mask under positive pressure. This type of equipment is normally used at altitudes above 40,000ft. A pressure demand mask must be worn with a pressure-demand regulator .by action of special pressure-compensating valves, the mask provides for a buildup of oxygen pressure from the regulator and creates the required input of oxygen into the lungs.PARTS OF AN OXYGEN SYSTEM: 1. Oxygen bottles.2. Regulators.3. Oxygen masks. OXYGEN BOTTLES:Oxygen cylinders, also called as oxygen bottles, are the containers used to hold the a/c gaseous oxygen supply. The cylinders may be designed to carry Oxygen at a high or low pressure.High-pressure cylinders are designed to contain oxygen at a pressure of approximate 1800psi. They are usually green in color. Low-pressure cylinders are painted yellowish and are designed to store oxygen at a maximum of 450psi.There are several type of cylinder valves1. The hand wheel type as a wheel on the top if the valve and operates like a wa

ter faucet2. Another type of valve is of the self-opening design when the valve is attached to the oxygen system, a check valve is moved off of its seat allowing the cylinder to charge the system3. A third type of valve is uses a cabin operated push-pull control to operate the control lever on the top of the valve. This eliminates the necessity of always of oxygen system charged but allows the pilot to activate the system whenever needed.Oxygen cylinders are often fitted with safely disks, which rupture if the pressure in the cylinder becomes too great (which is due to high ambient air temperature heating the cylinder).REGULATORS:Regulators for the pressure and flow of oxygen are incorporated in stored-gas systems because the oxygen is stored in high-pressure cylinders under pressures of 1800psi or more. The high pressure must be reduced to a value suitable for application directly to a mask or to a breathing regulator. This lower pressure is usually in the range of 279 and 517 kpa, depending upon the system.OXYGEN MASKS:Oxygen masks vary considerably in size, shape and design; however each is designed for either a demand system or a continuous flow system. A mask for a demand system must fit the face closely, enclosing both the mouth and nose and must form an airtight seal with the face. A mask for a constant-flow system is designed so that some ambient air is mixed with the oxygen. The complete mask usually includes an oronasal face piece; a reservoir bag, valves, a supply hose and a coupling fitting some models include a flow indicator in the supply hose.