Available for aviation use are standard cannulas, Oxymizer® cannulas, and face masks.
THREE kinds of breathing devices are used in aircraft oxygen equipment. Face masks, standard cannulas, and oxygen conserving cannulas. Special face masks can be used, under proper conditions up to 49,000 ft.. Cannula devices are very popular for general aviation use. Face masks create a communications problem with Center and with passengers as well. Special masks with built in microphones are required. Nose cannulas eliminate the communications problems since the mouth is exposed. However, the cannulas are limited to 18,000 ft..
The standard cannula device (Part No. BD405) is basically the same as a typical hospital cannula. Its obvious advantages are the users unrestricted ability to talk, eat, and drink. It is directly interchangeable with any oxygen face mask. Limited by FAA to 18,000 ft.. A child's cannula (Part No. BD407) is available.
The Oxymizer oxygen conserving cannula (Part No. BD503) is produced by Chad Therapeutics. Oxymizers are very popular and have been used in aviation for many years. The use of the Oxymizer easily doubles the normal duration of oxygen use at 18,000 ft. and triples the use at 10,000 ft.. The basic principle of the Oxymizer is to accumulate wasted oxygen while the user is exhaling. Oxygen is only needed when we inhale. We inhale only about 25% of our breathing process and exhale the remaining 75%. However the oxygen is flowing all the time. Therefor, we are wasting 75% of the oxygen. Instead of wasting oxygen, we divert this oxygen into a small reservoir attached to the Oxymizer. This looks something like a large mustache. Odd looking, but unusually quite comfortable to wear. While we are exhaling, the oxygen is now flowing into the reservoir. When ready to inhale, we have accumulated some free oxygen. Matter of fact, we have more oxygen than what we really need. With the A-3 or A-4 flow meter, we can lean out the mixture of oxygen to much lower flow rate, thus increasing the duration of the oxygen system. A special attachment fitting is installed on the Oxymizer to provide a convenient hose length and provide for ease of attaching the Oxymizer to the flow meter. This attachment allows easy use to change quickly to a face mask for high altitude use.
Two face mask units are offered. The standard mask (Part No. BD404) is suitable for use up to 25,000 ft.. A child's mask is also available (Part No. BD406). A built in microphone is not available, but many users simply cut a small hole in the side of the mask, and insert their boom mike. The small amount of leakage around a minimal size opening in the side of the mask is not significant. The mask is not recommended by someone who has a beard. The hair of the beard doesn't allow the mask to seal very well on the face.
Offered is the Scott/Sierra 249 mask with a microphone (Part No. SC249M). This mask has been manufactured for over 50 years. A common problem with masks with the built-in microphone is an echo or distortion of the signal produced by the microphone. The distortion is somewhat like what you would expect by talking with your hands over your mouth or talking into a barrel. The signal can be so bad that Center can't even understand what you are saying. Their are other masks with microphones that are cheaper. Those masks work fine, but the communications are poor with the microphone.
The Scott/Sierra 249 mask is offered with an optional dynamic microphone that is suspended inside the mask cavity so the microphone is placed right in front of your lips, just like a boom microphone. Normally the microphone is located flush inside a recess in the cavity of the mask. The combination of the dynamic microphone and its location next to your lips, eliminate the distortion. An excellent signal is produced. The Scott/Sierra 249 mask is expensive, but in our opinion it is the only mask/microphone combination that works well.
The Scott/Sierra 249 mask is the most comfortable mask produced. The mask is made from a soft silicon rubber with large amount of surface area that contacts your face. A double strap assembly is provided so two portions of the strap go over the head. One strap over the top of the head and the other around the back of the head. Glasses can be easily be worn with this mask. The mask can be used up to 40,000 feet but we recommend up to 35,000 ft. Above that we recommend a demand type mask. We do not offer such a mask, but can inform you about availability. The Scott/Sierra mask can also be purchased without the installed microphone (Part No. SC249).
We suggest that any pilots who fly over 25,000 ft. use the Scott/Sierra 249 mask. It produces the best seal possible. The mask seal above 25,000 ft. is very important. However, we do not recommend a bearded pilot use this mask, or any other type of mask, above 25,000 ft..
We also are offering a new high quality mask manufactured by Aerox. This mask is super comfortable and uses the only electret microphone in the industry. This gives you higher quality sound transmission. This mask is also designed and is considered to be a quick donning device. The mask is softer and conforms better to your face. Over time the silicon will actually form to fit specifically to your face. The mask is available in small, Medium, and large sizes. Nelson Oxygen Equipment recommends the purchase of this mask over the others on the market.
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