Composition of Oxygen. Oxygen includes 21% of the atmosphere at all altitudes. The remaining atmosphere consists of 78% nitrogen and 1 % traces of other gases. Oxygen under normal conditions is an odorless, colorless, tasteless, non-combustible gas. It is the most important single element on earth. At each breath we fill our lungs with air. Millions of tiny air sacs (known as “alveoli”) in our lungs inflate like tiny balloons. In the minutely thin walls enclosing each sac are microscopic capillaries through which blood is constantly transported, from the lungs to every cell in the body. The blood carries the oxygen extracted from the air in the lungs to every part of the body. Because the body has no way to store oxygen, it leads a breath-to-breath existence. The human body must have oxygen to convert fuel (the carbohydrates, fats, and proteins in our diet) into heat, energy, and life. The conversion of body fuels into life is similar to the process of combustion; fuel and oxygen is consumed, while heat and energy is generated. This process is known as “metabolism”. The rate of metabolism, which determines the need for and consumption of oxygen, depends on the degree of physical activity or mental stress of the individual. Not all people require the same amount of oxygen. A man walking at a brisk pace will consume about four times as much oxygen as he will while sitting quietly. Under severe exertion or stress, he could possibly be consuming eight times as much oxygen as resting.
Body oxygen levels can drop for a variety of reasons; the obvious ones are injury or disease. Air should have about 21 % oxygen, but, in the cities, it can drop to 10%. Ancient air bubbles that were trapped in amber have been analyzed as containing twice as much oxygen as we now have in our air. Tap water loses oxygen from chlorine, and from not being aerated. Cooking drives the extra oxygen out of vegetables. Have you noticed how many raw juice and vegetable health diets have been proposed over the years? Antibiotics kill friendly bacteria that produce H2O2 in the body. Processed and hydrogenated foods cause the circulatory system to spend more time hauling out toxins than carrying in oxygen. Why take a chance?
Unfortunately, if you’re like most everyone, your blood oxygen content is low. Why? First, there’s less available oxygen due to rampant tree destruction. In ancient times, your ancestors breathed fresh air, which contained more than 30% oxygen in the assimilatory 02form. Today, O2 molecules are becoming “bound up” by pollution. In humid areas or high altitudes, it’s worse. The same as with continuously re-circulated stale air from your home or office AC/Heater. Add all of this together, and you may be getting 21% or even less available O2, depending on your environment! That’s a significant loss! Secondly, you may have shallow breathing habits. If you haven’t deliberately learned to breathe properly, you aren’t bringing enough air into the lungs and you’re not assimilating it efficiently in order to obtain vital blood oxygen levels. When blood oxygen content is low, your body is slowed, weakened, and easily fatigued. You need extra coffee just to get going in the morning!
In a 24 hour day, the adult man uses… (approx.) 8 pounds of oxygen… ” – A. Schatz, discoverer of streptomycin, in Cancer News Journal, v.12, n.2, p.6, June 1977. The average man consumes 6 to 8 pounds of oxygen, 4 pounds of food, and 2 pounds of water. More oxygen goes into our bodies than the other two combined. I would say oxygen is important.
Some ancient cultures installed big pipes on hilltops and pumped fresh mountain air down to the congested cities below. First in Japan, and now in the U.S., they sell small bottles of oxygen complete with a little mask. Well-known Japanese department stores have even set up “oxygen bars”, where customers can inhale scented oxygen. Canned oxygen, aimed at the sports market, has been sold to athletes in sporting goods stores as of a few years ago. Tokyo’s Takashimaya department store said they sold more than 300 gift sets of oxygen during the 1987 December season. Several stores offer gift sets of oxygen combined with sporting goods, health drinks or mineral water. A five quart canister of95% concentrated oxygen, (weighing about six ounces) gives the impression that one is holding a can of nothing. But at $11 a can, you hope you’ve bought something. The can contains enough oxygen to last about two minutes, or 60 to 80 breaths. The companies producing the canister claim that they relieve post sports fatigue, and can be used to refresh your self while working or driving.
A normal healthy person who lives at higher altitudes has somewhat adapted to the effects of high altitude. However that person still must have supplemental oxygen above 12,500 feet, while flying. The effects of hypoxia may be lesser for that person at 12,500 feet, but the problems are still there.
You can go without food for days, water for hours, but if you are denied oxygen for only a few minutes you can’t survive. Oxygen is crucial to your system. Vision is impaired as low as 5000 feet especially at night (the FAA recommends oxygen at 5000 feet at night). All the physical processes of your body, such as circulation, assimilation, digestion, and elimination “run” on oxygen. As a result, oxygen helps your body produce energy, balance its metabolism, purify itself of wastes, and fights fatigue. Flying tired is not fun.
As the total atmospheric pressure decreases with altitude, the available oxygen pressure decreases in proportion, thus necessitating supplemental oxygen. A lack of sufficient oxygen will bring on Hypoxia. Symptoms of Hypoxia may begin as low as 5,000 feet with decreased night vision. The retina of the eye is affected by even extremely mild Hypoxia. At 8,000 feet, forced concentration, fatigue and headache may occur. At 14,000 feet, forgetfulness, incompetence and indifference makes flying without the proper supplemental oxygen quite hazardous. At 17,000 feet, serious handicap and collapse may occur. These effects do not necessarily occur in the same sequence or to the same extent in all individuals.
A FAA flight surgeon gave me an excellent definition on the term. Hypoxia. He called it “STUPIDITY”. What typically happens when experiencing serious Hypoxia symptoms, you get too stupid to realize that something is wrong. For the regular smoker (especially with older people), these effects all occur at much lower altitudes. A person at sea level, who regularly smokes a pack of cigarettes a day, may theoretically be at 7,000 feet. If that person were flying at 12,000 feet, the actual altitude experienced could be as much as 19,000 feet. Obviously an altitude requires the use of oxygen. A person’s age drastically effects night vision. A 60-year-old has only 1/3 of the night vision of a 20-year-old. Of importance, there is very little peripheral vision at night. The see and be seen concept of aircraft collision avoidance is obviously limited during night flying. It is recommended that if one were to go above 18,000 feet, that person should be on oxygen for at least for 30 minutes prior to going above 18,000 feet. The time on oxygen lets the oxygen and nitrogen levels stabilize properly. Suggest that if you know you are going above 18,000 feet from sea level at the maximum climb rate then put on the oxygen before takeoff. By the time you get to 18,000 it probably will have taken about 30 minutes.
The symptoms of hyperventilation and Hypoxia are somewhat related and often are misunderstood. The FAA defines hyperventilation as follows: “Hyperventilation, or over breathing, is a disturbance of respiration that may occur in individuals as a result of emotional stress, fright or pain”. The respiratory center of the brain reacts to the amount of carbon dioxide found in the blood stream. When you are in a physically relaxed state, the amount of carbon dioxide in your blood stimulates the respiratory center and your breathing rate is stabilized at about 12 to 20 breaths per minute. When physical activity occurs the body cells use more oxygen and more carbon dioxide is produced. Excessive carbon dioxide enters the blood and subsequently the respiratory center responds to this, and breathing increases in depth and rate to remove the over supply of carbon dioxide. Once the excess carbon dioxide is removed, the respiratory center causes the breathing rate to change back to normal. To check for Hypoxia or hyperventilation: Check your oxygen equipment immediately. See if there is oxygen and the flow is at the proper rate for the altitude you are. The use of Aerox flow meters will verify if your system is working properly. After three or four deep breaths of oxygen, the symptoms should improve markedly if the condition experienced was Hypoxia. (Recovery from Hypoxia is extremely rapid). If the symptoms persist, you should consciously slow your breathing rate until symptoms clear and then resume your normal breathing. You can also breathe into a bag, or talk aloud to overcome symptoms of hyperventilation. Under conditions of emotional stress, fright or pain, the pilot’s lung ventilation may increase, although the carbon dioxide output of the body cells remains at a resting level. As a result, he “washes out” carbon dioxide from his blood. The most common symptoms are dizziness; hot and cold sensations, tingling of the lips and hands, legs, and feet; rapid heart rate; blurring of vision; muscle spasms; sleepiness; and finally, unconsciousness. After becoming unconscious, the breathing rate will be exceedingly low until enough carbon dioxide is produced to stimulate the respiratory center. Hyperventilation occurs as a result of the body’s normal compensatory response to Hypoxia. However, excessive breathing does little good in overcoming Hypoxia. Several aircraft accidents have been traced to probable hyperventilation. It is recommended that you induce hyperventilation by voluntarily breathing several deeps breaths at an accelerated rate (not while flying). You will begin to get some of the symptoms mentioned. Once you experience several of these symptoms, return to your normal rate of breathing. After you become familiar with the early warnings your body gives you, the likelihood of an accident caused by hyperventilation will be reduced. Caution: Do not hyperventilate while alone or in a standing position. You may fall and injure yourself.
We have many pilots tell us women passengers need oxygen much sooner than they do. We are not talking high altitude either. Typically the problem seems to occur at around 9,000 to 10,000 feet. The symptoms for the women passengers are sleepiness and headaches. Several doctors have told us the reason for women to be affected by the beginning symptoms of Hypoxia is caused by a difference in their hemoglobin content in their blood. Of interest, women also experience different conditions in breathing requirements while scuba diving. We have received several orders for oxygen equipment mainly for women passenger use at these low oxygen altitudes. A good rule of thumb is that women normally need oxygen about 2,000 feet sooner than men. Of course there are exceptions. Another more obvious reason for more oxygen for passengers is due to nervousness of passengers who have had no or little experience flying in light aircraft. When one is nervous, the body is working harder, thus needing more oxygen.
Under normal conditions there is no need for supplemental oxygen in an aircraft equipped with a pressurized cockpit. However, there are conditions that can require additional oxygen. Many pressurized aircraft only bring the cabin altitude down to 10,000 feet. Many people are Hypoxia at 10,000 feet. The odds are that a heavy smoker will be Hypoxia when in a pressurized cabin. Some pilots have purchased portable systems to provide the additional need for oxygen. Recently we had a customer with a Cessna 340 (pressurized cabin twin) that has been complaining about fatigue while flying at 25,000feet. To solve his problem he is using the built in emergency constant flow system. The normal duration is not sufficient, but with the Aerox flow meter and oxygen conserving Oxysaver breathing device, he now has several hours of supplemental oxygen available to assist with his breathing needs.
This is the amount of time during which a pilot is able to effectively, or adequately fly his aircraft with an insufficient supply of oxygen. At altitudes below 30,000 feet this time may differ considerably from the time of total consciousness (the time it takes to pass out). Above 35,000 feet the time become shorter and eventually coincides, for all practical purposes, with the time it takes for blood to circulate from the lungs to the head. Average Effective Performance Time for flying personnel without supplemental oxygen: 15,000 to 18,000 feet 30 minutes or more 22,000 feet 5 to 10 minutes 25,000 feet 3 to 5 minutes 28,000 feet 2 1/2 to 3 minutes 30,000 feet 1 to 2 minutes 35,000 feet 30 to 60 seconds 40,000 feet 15 to 20 seconds 45,000 feet 9 to 15 seconds Factors which will determine the Effective Performance Time Altitude. EPT decreases at high altitudes. Rate of ascent. In general, the faster the rate, the shorter the EPT. Physical Activity. Exercise decreases EPT considerably. Day-to-day Factors. Physical fitness and other factors (smoking, health, or stress) may change your ability to tolerate Hypoxia from day to day, thereby changing your EPT.
There is a new breathing problem with the advent of the high rate of climb 250+ horsepower homebuilts. Sustained rates of climb in excess of 2,000 feet per minute are possible with the Glasair and Lancair type of aircraft. Total time to climb to 20,000 feet can be less than 10 minutes. Problem here is that the average person’s body cannot adapt to that change of altitude in that time period. I understand that it takes at least 20 minutes for the body to adjust to that change. The problem is nitrogen gas bubbles in the body. This is called “the Bends”, the same problem that can occur in deep sea diving. Extreme pain can occur and if a nitrogen gas bubble occurs in the brain, death can occur. Climbing to 25,000 feet makes the possibility of the bends even more so. Some people may make it to 20,000 feet OK, but an even greater number of people may not make it to 25,000 feet in these short time periods. To make things worse, there are no FAA requirements or recommendations about the effects of high rates of climb. Hopefully the FAA will and the manufactures of these aircraft will advise pilots about these problems. There are two ways of solving the problem for most situations. One is to limit the climb to 20,000 feet to less than 1,000 feet per minute. The other suggestion is to put on the oxygen soon as you start the engine and let your body start adapting sooner.
Oxygen Requirements at Altitude. The FAA requires that all pilots flying their aircraft above 12,500 feet for 30 minutes or longer or at 14,000 feet or above during the entire flight must use supplemental oxygen. The amount required is 1 liter of oxygen per minute for every 10,000 feet. For example, at 18,000 feet there should be a flow of 1.8 liters per minute of oxygen available via a standard breathing device. The FAA requires there should be a device so attached to each breathing device that visually shows the flow of oxygen. (Aerox flow meters meet this FAA requirement.) The FAA also regulates that passengers must have supplemental oxygen available over 15,000 feet and that it is recommended that supplemental oxygen be used at night at altitudes over 5,000 feet.
Strangely enough, the FAA does not have any publications available that cover the use of oxygen in general aviation. There is an excellent manual that is only given out when you go for an FAA Altitude Chamber ride.
We strongly recommend that anyone who uses or plans to use oxygen in aircraft attend one of the physiological training programs sponsored by the FAA and the military. Courses include inforn1ation on Hypoxia, hyperventilation, and as well as offering altitude-chamber rides, where you can safely experience your own reaction of oxygen deprivation. There is waiting list for the courses. The cost for the courses is minimal. Courses are offered at many military bases around the country. You can get an application form by writing or calling the FAA Civil Aeromedical Institute, Airman Education Section AAM-420, PO Box 25082, Oklahoma City, Okla. 73125, (405) 686-4837. Better yet, contact your local FAA Accident Prevention Specialist and ask for AC Form 3150-7.
An expensive aircraft modification to gain a few knots per hour in performance is one way of increasing ground speed. But flying higher taking advantage of thinner air and favorable wind conditions not only increase ground speed but also improves fuel consumption. We have experienced a tremendous difference in flying at 7,000 feet and 14,000 feet. Portable oxygen systems cost as little as $500.00 not the thousands the modifications cost.
Handling and Refilling
There are three kinds of oxygen that are merchandised or sold to users; Aviator Breathing, USP Medical, and Welding. All three types must be 99.5% pure. Oxygen gas is produced from the boiling off of liquid oxygen. It would appear that the oxygen is therefore the same. Where we obtain oxygen, all the different types of oxygen are supplied from the same manifold system. It has been said that USP oxygen has moisture in it. That is not true. The oxygen going to a hospital bed is pure oxygen that comes from liquid oxygen. At the bed location, there may be a humidifier that adds moisture. The cost of USP or welding oxygen is normally much less than the oxygen you get at an airport. The bottom line about the different types of oxygen is in the insurance liability of the oxygen supplier. The gas is the same but the insurance liability is different. The welding Gas Company mayor may not supply you with oxygen for your aircraft. Likewise the medical oxygen supplier mayor may not supply you with oxygen for your aircraft. Some of our customers have told us that they can only get medical oxygen for aircraft use if they have a prescription from their family doctor. We ask you to determine if the welding or medical oxygen is suitable for your use. We do not and cannot make any recommendation on the use of oxygen other than aviation oxygen.
The use of oxygen in general aviation is quite safe. The use of it is done on a regular basis throughout the world. Reading the manufacturers instructions and going by them, as well as the use of common sense, make oxygen use practical. The use of oxygen, no different than the use of the aircraft itself, does have some potential problems. In that light, the following information is important and should be remembered when dealing with oxygen. Although oxygen is non-flammable, materials which burn in air will burn much more vigorously, and at a higher temperature, in oxygen. If ignited some combustibles such as oil, burn in oxygen with explosive violence. Some other materials, which do not burn in air, will burn vigorously in oxygen-enriched atmospheres. A hazardous condition does exist if high pressure oxygen equipment becomes contaminated with hydrocarbons such as oil, grease, or other combustible materials which may include oil from the operator’s hands or contaminated tools. Oxygen under pressure presents a hazard in the form of stored energy. Rapid release of high- pressure oxygen through orifices, needle valves etc. in the presence of foreign particles can cause friction or impact resulting in temperatures which may be sufficient to ignite combustible materials and rapidly oxidize metals. A cylinder will heat as it is filled from a high-pressure source, due to the heat of compression generated as gas is forced into the cylinder. The more rapidly the cylinder is filled the higher temperature rise in the cylinder. Excessive temperature may result in ignition of any combustible materials that are present.
A gas manufacturer, gas distributor must refill containers, or someone qualified in the refilling of aircraft oxygen cylinders. The markings stamped into cylinders shall not be removed or changed. The user shall not deface or remove any markings, labels, decals, tags or stencil marks applied by the supplier and used for identification of content. The user shall not change, modify, tamper with, obstruct or repair the pressure-relief devices, container valves or in containers. The user shall not repair or alter containers or container valves. Any other damage noted that might impair the safety of the container shall be called to the attention of the gas supplier refilling the container.
Containers should not be used as rollers, supports or for any purpose other than to contain the appropriate contents. The user should keep container valves closed at all times (charged or empty) except when the container is in use.
Compressed gas containers should not be subjected to atmospheric temperatures above 130 degrees F. A flame shall never be permitted to come in contact with any part of a compressed gas container. Containers shall not be stored near readily ignitable substances such as gasoline or waste papers, or near combustibles including oil. Containers shall not be exposed to continuous dampness nor be stored in the sun.
Only properly trained persons shall handle compressed gases. The user responsible for the handling of the container and connecting it for use shall check the identity of the gas by reading the label or other markings on the container before using. If container content is not identified by marking, the container shall be returned to the supplier without using it. Container color shall not be relied upon for content identification. Connections that do not fit should not be forced. Threads on regulator connections or other auxiliary equipment should match those on container valve outlet. Regulators, gauges, hoses and other appliances provided for use with a particular gas or group of gases should not be used on containers containing gases having different chemical properties unless information obtained from the supplier indicates that this can be done safely. As an example, only pressure-regulating devices approved for use with oxygen should be used in oxygen service.
Container valve should be opened slowly for safety. Valve outlets should be pointed away from yourself and other persons. Valve wheels or levers should not be hammered in attempting to open or close the valve. For valves that are hard to open, or frozen because of corrosion, the supplier should be contacted for instructions. Before a regulator is removed from a container, the container valve should be closed and the regulator drained of gas pressure. Oxygen containers, valves, regulators, hose and other oxygen apparatus should be kept free from oil or grease and shall not be handled with oily hands, oily gloves or with greasy equipment.