 A very important issue affecting safe flight is the proper use of oxygen equipment. Practical knowledge about oxygen systems is necessary because oxygen should be readily available whenever it is needed. Because instruction on the use of oxygen equipment is not readily available, this module will summarize for you the physiological requirements and proper use of personal aviation oxygen equipment. This pertains to all general aviation aircraft, whether pressurized or unpressurized. Some operational precautions to use with all oxygen systems are Keep your oxygen equipment clean. For proper cleaning instructions, check with the manufacturer of the mask. The interaction of oil-based products with oxygen creates a fire hazard. Additionally, oil attracts dirt particles, which contaminate storage containers, regulators, masks and valves. Protect your oxygen mask from direct sunlight and excess dust. Store masks properly. Inspect your portable oxygen storage containers to make sure that they are securely fastened in the aircraft. Turbulence or abrupt changes in aircraft attitude can cause them to come loose. Do not allow anyone to smoke around oxygen equipment that is being used or when maintenance is being performed. Oxygen supports and rapidly accelerates the combustion of all flammable material. Ensure that the aircraft is properly grounded before loading oxygen. Make sure your oxygen equipment is inspected regularly at an authorized FAA inspection station. Be cautious of interchanging components of oxygen systems. Ensure that all components, storage, regulators and masks are compatible. The aviation industry has designed and manufactured widely diverse types of oxygen equipment for the general aviation aircraft. Pilots who routinely fly at altitudes above 10,000 feet mean sea level commonly use a fixed oxygen system. Fixed systems are normally serviced through an exterior fuselage valve. The major advantage of a fixed oxygen system is greater oxygen storage capacity. A portable oxygen system is a self-contained unit that can be taken on and off the aircraft. This system is designed especially for short duration flights at altitudes above 10,000 feet mean sea level. One disadvantage of portable oxygen equipment is its relatively limited oxygen supply. Regardless of the type of oxygen system used, duration of oxygen supply depends upon several factors. The size of the oxygen container, the altitude of the flight, the number of people using the oxygen system. There are three components on most oxygen systems, whether they are portable or fixed. Storage systems, regulators, oxygen mask or nasal cannulus. There are three ways to store oxygen, gaseous state, liquid state, solid state. Gaseous oxygen can be stored in low pressure containers at the standard pressure of 400 to 450 pounds per square inch or in high pressure containers at 1800 to 2200 pounds per square inch. Primarily high pressure systems are used in both commercial and general aviation. Liquid oxygen is stored at extremely cold temperature minus 183 degrees Celsius or minus 297 degrees Fahrenheit. As the liquid passes through warming coils, it converts to a gaseous state. A practical approach to the storage of oxygen is in a solid state form. Oxygen is generated by a chemical reaction process. The storing of oxygen in a solid state form is used in both general and commercial aviation. The body's blood oxygen saturation level, the capacity of the blood to transport oxygen, is normally between 96 and 98 percent. To maintain this level, as you ascend to altitude, your body must receive a correspondingly higher oxygen flow rate and percentage of oxygen. Regulators help in determining the proper oxygen flow. Most types fall into one of two categories, continuous flow or diluter demand. There are three types of continuous flow regulators. The fixed flow system delivers oxygen continuously once the system is activated. The amount of oxygen flow is determined by three factors. The type of continuous flow system in use. The orifice size coming out of the container. The orifice size on the plug-in adapter in the end of the mask hose. The primary disadvantage of a continuous flow system is its inability to adjust automatically to the changing needs of the pilot level of physical exertion or altitude changes during flight. The second type of continuous flow regulator incorporates a manual adjustment knob. This allows the user to increase or decrease the oxygen flow rate corresponding to aircraft cabin altitude or physical exertion, ensuring proper blood oxygen saturation and efficient use of the oxygen supply. The third type of continuous flow regulator uses an aneroid control to automatically increase or decrease the oxygen flow rate corresponding only to the aircraft cabin altitude. The increase in the operational altitudes of aircraft dictated improvements in oxygen regulators. To increase efficiency and keep the body physiologically safe at higher altitudes, the diluter demand regulator was developed. Diluter demand regulators furnish oxygen when the user inhales. It also incorporates an auto-mix lever, enabling the user to select either a mixture of cabin air and oxygen or 100% oxygen. In the normal oxygen setting, the regulator uses an aneroid control to automatically adjust the percentage of oxygen delivered. These improvements have increased the operational effectiveness of such oxygen equipment to 34,000 feet mean sea level. For further improvements in aircraft operational performance, a more efficient regulator was needed. The answer was the pressure demand regulator. The pressure demand regulator functions the same as the diluter demand regulator with one additional feature. It delivers oxygen under positive pressure to maintain blood oxygen saturation at the higher altitudes. The pressure demand regulator used in general aviation is certified to 45,000 feet mean sea level. Summing up, you must ensure that there is adequate oxygen flow and the proper percentage of oxygen is being received for the altitude you are flying to protect against hypoxia. The third part of any oxygen system is an oxygen mask or nasal cannulus. General aviation continuous flow oxygen masks come in two types, rebreather and phase sequential. The rebreather type is the most common, the least expensive, and is the simplest to use. It has an external plastic bag that inflates every time you exhale. The purpose of the bag is to store exhaled air so it can be mixed with 100% oxygen from the system. This type of mask supplies adequate oxygen to keep the user physiologically safe up to 25,000 feet mean sea level. The mask should seal properly to the face. The phase sequential continuous flow mask is a passenger mask that looks similar to a rebreather mask. These masks have reservoir bags for the supply of oxygen coming into the mask, a dilution valve which permits entry of outside air after the bag has been drained of its oxygen, and an exhalation valve which dumps air overboard when the user exhales. During exhalation, the reservoir bag is supplied with oxygen from the regulator in preparation of the next breath. This mask provides 100% oxygen at the beginning of the inhalation cycle and a dilution with outside air at the end of the inhalation cycle. The user does not rebreathe any exhaled air. With the proper flow rate, the phase sequential mask will supply adequate oxygen for a short duration emergency at altitudes up to 40,000 feet mean sea level. Nasal cannulus are also continuous flow devices and offer the advantage of being more comfortable. They are restricted by federal aviation regulations to 18,000 feet surface altitude because blood oxygen saturation levels can decrease if one breathes through the mouth or talks too much during flight. With increased aircraft technology and altitude ceilings, two additional masks were developed. The diluter demand mask is designed to facilitate an air and oxygen tight seal to the face. The amount of oxygen inhaled through the mask is dependent upon the altitude and the setting of the auto mix lever. The latest generation of oxygen mask is referred to as pressure demand. These masks are designed to create an airtight oxygen seal on the face. The inhalation and exhalation valves are designed to permit oxygen pressure to build up within the face mask, thus supplying oxygen under pressure to the lungs. Quick Dawn Crew oxygen masks have a quick release holding strap or a quick release storage container that allows for rapid access to the mask. During an emergency situation requiring the use of oxygen, the pilot should be able to release and dawn the mask within five seconds. If you are not familiar with the requirements concerning oxygen use in your particular operation, contact the FAA Flight Standards District Office nearest you. Warning! Masks have not been qualified for wear over beards or heavy facial hair growth in accordance with FAA technical standard orders. Facial hair that crosses ceiling surfaces can seriously degrade the performance of these masks. Prior to every flight, you should perform the price check. The price is a checklist that helps pilots and crew members inspect oxygen equipment. Pressure! Ensure that there is enough oxygen pressure and quantity to complete the flight. Regulator! Inspect the oxygen regulator for proper function. If you are using a continuous flow system, make sure the outlet assembly and plug-in coupling are compatible. Indicator! Most oxygen delivery systems indicate oxygen flow through the use of flow indicators. Flow indicators may be located on the regulator or within the oxygen delivery tube. You should check the flow indicator whenever the oxygen mask is donned to assure a steady flow of oxygen. Connections! Ensure that all connections are secured. This includes oxygen lines, plug-in coupling, and the mask. Emergency! Have oxygen equipment in the aircraft ready to use for those emergencies that call for oxygen, hypoxia, decompression sickness, smoke and fumes, and rapid decompressions. This step should include briefing passengers on oxygen location and proper use. Most of the oxygen sold today in the U.S., including aviation oxygen, is produced by a cryogenic method using sub-freezing temperatures. This method produces an oxygen purity of 99% or higher. Aviation oxygen is subject to a process that removes water vapor. For safety's sake, it is recommended that you double-check that you are getting oxygen that was produced cryogenically. Purchase the liquid oxygen as close to the production site as possible to eliminate transportation contamination. You are responsible for checking with the equipment manufacturer for the latest operational and emergency sealing of the equipment to assure your safety. By following the necessary precautions and knowing how to operate your oxygen equipment effectively, you will be able to fly more confidently and more safely. Operational precautions when dealing with oxygen. Keep your oxygen equipment clean. Protect your oxygen mask from direct sunlight and excess dust. Inspect your oxygen storage containers. Do not allow anyone to smoke around oxygen equipment. Make sure your oxygen equipment is inspected regularly. Be cautious of interchanging components of oxygen systems. Prior to every flight, the pilot should perform the price check. Pressure. Ensure there is enough oxygen pressure and quantity to complete the flight. Regulator. Inspect the oxygen regulator for proper function. Indicator. Check the oxygen flow indicator to assure that there is a steady flow. Connections. Ensure that all connections are secured. Emergency. Have oxygen equipment in the cockpit and ready to use for those emergencies that call for oxygen. You are responsible for checking with the equipment manufacturer for the latest operational and emergency sealing of your oxygen equipment to assure your safety.