CR4® - The Engineer's Place for News and Discussion®


Previous in Forum: New Outlook about Death   Next in Forum: What is This?
Close
Close
Close
31 comments
Member

Join Date: Jul 2015
Posts: 8

Oxygen Concentrator Use for Nitrogen Concentration

07/21/2015 12:15 PM

I'm interested in generating a moderate flow of hypoxic atmospheric gas for the purpose of physiologic altitude acclimatization. That is, I need to either remove some O2 from air or add N2 to air to achieve, for example an O2 fraction of 12 to 15% at a flow of up to 50 LPM. There are commercial machines used for this exact purpose however they are very expensive. It occurs to me that the waste gas from an O2 concentrator should have a diminished O2 concentration and might be used in the development of such a machine.

Home medical O2 concentrators use a process called pressure swing adsorption (PSA) onto a product called zeolite, which has an affinity for N2. The basic concept is that compressed air is pushed through a zeolite sieve and mostly O2 exits this chamber. A few valves are thrown and the machine is cycled and the chamber is evacuated, renewing the zeolite then the process repeats. The cycle time is less than ten seconds.

It would make sense, for example, that a (typical home medical) machine that can deliver 10 LPM of O2, must also discard an extra 80 LPM of N2, just about right for my application. However, there is no guarantee that this is pure N2. The waste gas certainly would have some O2 in the mixture but I don't know whether the waste gas mix would contain 1% O2 or even 15% or more O2. I can deal with any concentration of 10% O2 or less since the maximum altitude simulation I want to achieve would require a minimum concentration of 10%. To achieve a higher FiO2 using an excessively hypoxic waste gas concentration, I simply would need to add ambient (21%) air at the appropriate rate.

Used O2 concentrators are commonly available at minimal cost.

Do you have any advice based on any use, repair or knowledge of O2 concentrators as to whether this idea for creating a hypoxic atmospheric gas generator in this fashion is feasible?

Thanks for reading and I'll tell you in advance that I have the medical and biomedical / electronic and physiologic knowledge and experience to build this and to do this safely. I'm just looking for any useful tips on the nature of the waste gas output from a home O2 concentrator.

Register to Reply
Interested in this topic? By joining CR4 you can "subscribe" to
this discussion and receive notification when new comments are added.

Comments rated to be Good Answers:

These comments received enough positive ratings to make them "good answers".

Comments rated to be "almost" Good Answers:

Check out these comments that don't yet have enough votes to be "official" good answers and, if you agree with them, rate them!
2
Guru

Join Date: Mar 2007
Location: at the beach in Florida
Posts: 19210
Good Answers: 1125
#1

Re: Oxygen concentrator use for nitrogen concentration

07/21/2015 12:30 PM

Wouldn't physical conditioning be the best way to prepare?

http://www.alpineinstitute.com/articles/physical-conditioning-for-mountaineering-expeditions/

I can't see how limiting oxygen is useful or even safe, in fact it seems to me a dangerous and risky venture...

__________________
Life is like riding a bicycle. To keep your balance you must keep moving. A.E.
Register to Reply Good Answer (Score 2)
Guru
Technical Fields - Technical Writing - New Member Engineering Fields - Piping Design Engineering - New Member

Join Date: May 2009
Location: Richland, WA, USA
Posts: 19977
Good Answers: 749
#2

Re: Oxygen Concentrator Use for Nitrogen Concentration

07/21/2015 12:36 PM

A little dab of CO might get you to the same destination. Not advisable.

__________________
In vino veritas; in cervisia carmen; in aqua E. coli.
Register to Reply
Guru

Join Date: Oct 2008
Posts: 39867
Good Answers: 1586
#3

Re: Oxygen Concentrator Use for Nitrogen Concentration

07/21/2015 12:49 PM

Why are you here if you already, "have the medical and biomedical / electronic and physiologic knowledge and experience to build this and to do this safely".

I'd be talking to companies who build O2 generators.

Or experimenting with the used ones, with a second person observing (with O2 tank at the ready) if you are too successful in the experiments.

Register to Reply
Guru
Canada - Member - If there is a way to screw someting up, there is someone to do so! Safety - Hazmat - New Member

Join Date: Mar 2007
Location: Iqaluit, NU. Canada
Posts: 1811
Good Answers: 137
#4

Re: Oxygen Concentrator Use for Nitrogen Concentration

07/21/2015 1:44 PM

While it certainly sounds like you have the knowledge to do this... I sure as heck suggest you do not. Go get a purpose built piece of gear. This really does sound to me like the opening parragraphs of a future Darwin Award narrative.

__________________
Joe Contractor to Electrical Inspector, "What do you mean you are going to make me follow the code?".
Register to Reply
Guru
United Kingdom - Member - Indeterminate Engineering Fields - Control Engineering - New Member

Join Date: Jan 2007
Location: In the bothy, 7 chains down the line from Dodman's Lane level crossing, in the nation formerly known as Great Britain, and now disconnecting as Little England and Wales (not too sure about Wales bit, either). Kettle's on.
Posts: 26689
Good Answers: 700
#5

Re: Oxygen Concentrator Use for Nitrogen Concentration

07/21/2015 2:09 PM

Perhaps the survivor(s) might add to this thread with some narrative as to how successful the equipment was? It's only that, those who did not survive, would not be able to do so.

__________________
"Did you get my e-mail?" - "The biggest problem in communication is the illusion that it has taken place" - George Bernard Shaw, 1856
Register to Reply
Guru

Join Date: Jun 2009
Location: South of Minot North Dakota
Posts: 8399
Good Answers: 771
#6

Re: Oxygen Concentrator Use for Nitrogen Concentration

07/21/2015 2:41 PM

Well since I actively promote the Darwin awards, especially so for fitness freaks, My suggestion would be to seal off your exercise room with plastic and get yourself a dewar of liquid nitrogen and have a fan circulate the air in the room while the liquid nitrogen boils off thus reducing the average oxygen content of the room.

Supervision and oxygen monitor optional of course.

Register to Reply Score 1 for Good Answer
Guru

Join Date: Jun 2011
Location: Phnom Penh
Posts: 4041
Good Answers: 104
#18
In reply to #6

Re: Oxygen Concentrator Use for Nitrogen Concentration

07/22/2015 12:10 AM

Could also seal the room and light a fire.

That would consume the oxygen faster than the nitrogen would dilute it. When the fire goes out open the window.

__________________
Difficulty is not an obstacle it is merely an attribute.
Register to Reply Score 1 for Off Topic
Power-User

Join Date: Feb 2007
Posts: 276
Good Answers: 25
#19
In reply to #18

Re: Oxygen Concentrator Use for Nitrogen Concentration

07/22/2015 12:38 AM

Now, THAT was funny!

Register to Reply
Guru
Technical Fields - Project Managers & Project Engineers - New Member

Join Date: Aug 2006
Location: Midwestern United States
Posts: 830
Good Answers: 73
#7

Re: Oxygen Concentrator Use for Nitrogen Concentration

07/21/2015 2:46 PM

Typically, the intended output of any device is what is regulated/controlled to a measurable level. Whereas the exhaust is a byproduct of the process and is not generally controlled.

Sounds to me like you're trying to take the uncontrolled byproduct of a process and use it to create a controlled environment... possible? If the input to the process is controlled, and the unit functions within some acceptable capability range (maybe perform an SPC analysis of the exhaust and see if you get an acceptable Cpk capability index that meets your needs.

__________________
Reuters - Investigators found that the recent thread derailment in CR4 was caused by over-weight creatures of lore and request that membership DON'T FEED THE TROLLS.
Register to Reply
Member

Join Date: Jul 2015
Posts: 8
#8

Re: Oxygen Concentrator Use for Nitrogen Concentration

07/21/2015 3:35 PM

Physical conditioning and altitude acclimatization are (unfortunately) two totally independent factors for determining performance at altitude. Thank you, the article you cite has some great suggestions for one who has not done any physical preparation for an event. Unfortunately, physical conditioning does not guarantee acclimatization and altitude acclimatization (obviously) does not improve physical conditioning. I understand your concerns on limiting oxygen. It must be done with monitoring on the gas delivery and patient side with fail safe features at several levels.
I am limited to training at sea level.
Partial gas pressure is all your body recognizes with respect to the gas exchange in the lungs and tissues. That is why Apollo astronauts used 1/3 atm of 100% O2 and why deep waters divers at 100m can use just a few percent O2. Breathing 14% oxygen at sea level is about as risky as . . . traveling to Colorado.
Re your question "why am I here?" That was stated in the last paragraph.
"Do you have any advice based on any use, repair or knowledge of O2 concentrators as to whether this idea for creating a hypoxic atmospheric gas generator in this fashion is feasible?"
Perhaps someone has worked with these machines or has used PSA technology for some related task and can provide some useful feedback.
There is a thread on your forum re O2 concentrators that comes up in a google search. One person was refilling the zeolite adsorber and was asking for (and receiving) advice. That was why I chose this form to post the question.
The first few paragraphs were just to give you some background to the discussion.
I've designed, built and used physiologic monitors and medical gas delivery systems for almost 35 years but I haven't ever used or dissected an O2 concentrator.
Java, yes the waste gas might have some variability, probably cyclic with the machine cycles. I would expect to use some sort of tank or expandable container to buffer the output. Use an O2 cell to measure it in order to make real time flow adjustments then another O2 cell on the final mixture. Oximetry is generally used on the trainee and is sometimes used as feedback to the controller. Additional user failsafe or vigilance switches require a responsive user to allow the machine to continue operation.

Register to Reply Score 1 for Good Answer
Guru

Join Date: Mar 2007
Location: at the beach in Florida
Posts: 19210
Good Answers: 1125
#9
In reply to #8

Re: Oxygen Concentrator Use for Nitrogen Concentration

07/21/2015 7:34 PM

OK I get it...Your trying to build a cheaper version of a nitrogen generator....I didn't know this was a thing...still not sure if it's a good idea, or even safe...

http://www.nitrogen-generators.com/nitrogen-generators-how-it-works/

http://www.pureairemonitoring.com/pureaires-o2-monitor-used-in-high-altitude-training-gains-recognition-among-athletes/

__________________
Life is like riding a bicycle. To keep your balance you must keep moving. A.E.
Register to Reply
Power-User

Join Date: Nov 2008
Location: Seoul, Republic of Korea
Posts: 287
Good Answers: 26
#10

Re: Oxygen Concentrator Use for Nitrogen Concentration

07/21/2015 7:41 PM

the answer to your question would lie in analysing a PSA over the course of a full pressure swing cycle

A PSA will be specified with a feed rate X AM3/hr (actual m3/hr) to produce a rate of Y Am3/hr O2 at a C1 concentration

The waste stream will average out to (X-Y) Am3/hr

The Oxygen feed is 0.21 * X

The oxygen in the waste is 0.21 X - Y C1

You must ensure that you take averaged figures over the course of the PSA cycle

__________________
Free advice guaranteed or your money back
Register to Reply
Member

Join Date: Jul 2015
Posts: 8
#11

Re: Oxygen Concentrator Use for Nitrogen Concentration

07/21/2015 8:55 PM

Thanks, SimonSD and SolarEagle. I'll give it a closer look later tonight. But perhaps the device could be built even from scratch with the right components. There are N2 generators readily available for commercial production and for food processing (flushing O2 from packages) but they are for serious production and some take up entire buildings ($100k on Alibaba!)

Register to Reply
Guru

Join Date: Mar 2007
Location: at the beach in Florida
Posts: 19210
Good Answers: 1125
#14
In reply to #11

Re: Oxygen Concentrator Use for Nitrogen Concentration

07/21/2015 10:27 PM
__________________
Life is like riding a bicycle. To keep your balance you must keep moving. A.E.
Register to Reply Score 1 for Good Answer
Guru

Join Date: Oct 2008
Posts: 39867
Good Answers: 1586
#12

Re: Oxygen Concentrator Use for Nitrogen Concentration

07/21/2015 9:07 PM

Is this device to be used in a clinical setting or in the field?

For a single patient/user/trainee?

Pharmacologic stress testing?

Have you stated the purpose of the device beyond the reduction of inhaled oxygen?

Register to Reply
Guru

Join Date: Jun 2009
Location: South of Minot North Dakota
Posts: 8399
Good Answers: 771
#13

Re: Oxygen Concentrator Use for Nitrogen Concentration

07/21/2015 10:04 PM

Another cheap way to limit your oxygen intake would be to simply cloths pin your nose shut and put a piece of heavy tape over you mouth with a small hole in it that lets just enough air in and out to keep you from completely blacking out when you exert yourself.

Register to Reply
Guru
Technical Fields - Technical Writing - New Member Engineering Fields - Piping Design Engineering - New Member

Join Date: May 2009
Location: Richland, WA, USA
Posts: 19977
Good Answers: 749
#21
In reply to #13

Re: Oxygen Concentrator Use for Nitrogen Concentration

07/22/2015 3:06 AM

Even easier, just visit Guantanamo and get water-boarded.

__________________
In vino veritas; in cervisia carmen; in aqua E. coli.
Register to Reply
Member

Join Date: Jul 2015
Posts: 8
#15

Re: Oxygen Concentrator Use for Nitrogen Concentration

07/21/2015 10:36 PM

lyn, this

http://go2altitude.com/pro_oneplus.php

is what I'm trying to emulate, but I can't fork out $15,000 for it!

I'm not trying to get it approved for medical use of any kind of market. Just want to use it myself for altitude mountaineering conditioning at sea level. Can't afford to take off for a month to do it on location.

Hey Tcmtech - that is exactly what the really cheap products do and they claim to be 'hypoxic trainers'. There is no hypoxic training, just extra lung work.

That's what this guy is wearing and he calls it hypoxic training.

https://www.youtube.com/watch?v=dkN1Iz7QJbs

Not sayin' there's not some benefit to it, but he's just breathing ambient air and the dead space of that tiny mask isn't enough to reduce O2 concentration.

Register to Reply
Guru

Join Date: Oct 2008
Posts: 39867
Good Answers: 1586
#16
In reply to #15

Re: Oxygen Concentrator Use for Nitrogen Concentration

07/21/2015 11:01 PM

I don't understand why you rock hoppers tempt fate and risk death for the thrill of it.

I can't help you.

You are far more qualified to do this than I.

Good luck.

Annapurna? K2? The big one?

What have you done?

Do they still use these?

Register to Reply
Guru

Join Date: Mar 2007
Location: at the beach in Florida
Posts: 19210
Good Answers: 1125
#17
In reply to #15

Re: Oxygen Concentrator Use for Nitrogen Concentration

07/21/2015 11:45 PM

Couldn't you just breath into a bag until you feel the effects ever so often....?

Hey! I'd put a hole in that bag before you,,,,,oh,,,,,too late....

__________________
Life is like riding a bicycle. To keep your balance you must keep moving. A.E.
Register to Reply
Member

Join Date: Jul 2015
Posts: 8
#20

Re: Oxygen Concentrator Use for Nitrogen Concentration

07/22/2015 12:51 AM

I know I said mountaineering but I'm actually training for trail running races. The rock climbing looks fun, but I don't quite have the bandwidth to train for that as well.

And . . . good question about the bag rebreathing. You would indeed achieve hypoxia but also hypercarbia. That is, you accumulate CO2.

Two ways to get around CO2 elimination

1) breathe fresh gas with each breath, in which case you need fresh gas flow greater than your minute ventilation - advantage - no soda lime, simple circuit. disadvantage, high gas flows

2) rebreath recirculated, exhaled air minus the CO2 through the use of a CO2 scrubber such as soda lime - advantage low gas flow, preservation of gas moisture. disadvantages - complex breathing circuit with two valves and return gas line and a consumable component of soda lime. This is what is used in the diving rebreathers and anesthesia breathing circuits.

Register to Reply
Guru

Join Date: Sep 2009
Posts: 967
Good Answers: 84
#22

Re: Oxygen Concentrator Use for Nitrogen Concentration

07/22/2015 5:17 AM

Brake some water through electrolysis, release produced O2 out of your environment and re-burn the remaining H2 in it. This should only change your O2 concentration and release some humidity. Patent pending (LOL) S.M.

__________________
Life is complex. It has a real part and an imaginary part.
Register to Reply
Guru
Canada - Member - Specialized in power electronics

Join Date: Feb 2008
Location: Montreal, Canada.
Posts: 1325
Good Answers: 78
#23

Re: Oxygen Concentrator Use for Nitrogen Concentration

07/22/2015 9:15 AM

You can buy nitrogen gas in a tank and use a proper regulator and flow meter to replace a fraction of your air intake using a mask. Just make sure it is pure nitrogen (food grade or medical). Don't use a welding grade as there may be other substances that you don't want in there. Your local gas supplier should have all the necessary equipment.

As other said, be careful as this is very dangerous.

Nitrogen over supply doesn't trigger any reaction in the body (gasp or similar). You simply faint and may die...

__________________
Experienced is earned, common sense is taught, both are rare essentials of life.
Register to Reply Score 1 for Good Answer
Guru

Join Date: Jan 2006
Location: Tamworth, UK.
Posts: 1531
Good Answers: 35
#24

Re: Oxygen Concentrator Use for Nitrogen Concentration

07/22/2015 9:23 AM

Have a look at membrane dryers used in the compressed air industry. They lower the dewpoint by removing water vapour molecules from the compressed air by a reverse osmosis process. They are very simple in-line devices and work like filters.

The technology is applied to similar devices (with the appropriate membrane material) that are available to separate O2 or N2 used in the diving industry (Nitrox devices).

Similar devices exist for the food industry to reduce O2 and water to preserve food in packets, and also by garages to fill car tyres.

I hope this helps.

__________________
When arguing, remember mud-slinging = lost ground.
Register to Reply
Guru
Hobbies - Musician - Engineering Fields - Chemical Engineering - New Member Engineering Fields - Control Engineering - New Member Engineering Fields - Instrumentation Engineering - New Member

Join Date: Jan 2007
Location: Moses Lake, WA, USA, Thulcandra - The Silent Planet (C.S. Lewis)
Posts: 3929
Good Answers: 174
#25

Re: Oxygen Concentrator Use for Nitrogen Concentration

07/23/2015 12:22 AM

As has been said, you need to be very careful. I believe that marcot had the best answer. What has not been said or asked is that you need to have someone you can trust to monitor you while you are breathing the "rarified air". Do you?

__________________
"Reason is not automatic. Those who deny it cannot be conquered by it. Do not count on them. Leave them alone." - Ayn Rand
Register to Reply
Member

Join Date: Jul 2015
Posts: 8
#26

Re: Oxygen Concentrator Use for Nitrogen Concentration

07/23/2015 2:35 PM

Marcot, Good point!That had crossed my mind a while ago but I thought it might not be economical. Turns out to be a reasonable solution when you look at the numbers.
125 CF N2 cylinder refill - $30 for 3,538 liters of N2Minimum O2 concentration needed: 15%, a 25% air dilution with N2Mixed with air yields 14,155 liters of 15% O2 in N2Minute ventilation with high level exercise 100LPM, typically 50 LPMYields ~2.4 to 4.8 hrs of intense exercise or around 24 hrs of treatment at rest.This would be a reasonable and easy solution and could be retrofitted with an N2 generator at some point if needed.As I mentioned, to be safe, it would need monitoring at multiple points of gas flow.
A built in gas flow fail safe as as well as flow ratio proportioner (seen with anesthesia gas systems) could work. Loss of O2 (air in this case) supply pressure shuts down all hypoxic gases.

Register to Reply
Guru
Canada - Member - Specialized in power electronics

Join Date: Feb 2008
Location: Montreal, Canada.
Posts: 1325
Good Answers: 78
#27
In reply to #26

Re: Oxygen Concentrator Use for Nitrogen Concentration

07/23/2015 2:46 PM

Even simpler,

Ask your local gas supplier to produce a final mixture according to your specifications.

Some suppliers will do that for a small supplement and you don't have to worry about meeting the recipe.

__________________
Experienced is earned, common sense is taught, both are rare essentials of life.
Register to Reply
Guru
Canada - Member - If there is a way to screw someting up, there is someone to do so! Safety - Hazmat - New Member

Join Date: Mar 2007
Location: Iqaluit, NU. Canada
Posts: 1811
Good Answers: 137
#29
In reply to #27

Re: Oxygen Concentrator Use for Nitrogen Concentration

07/23/2015 4:02 PM

I can see a commercial supplier running for the hills if presented with the reason behind the need for this material.

__________________
Joe Contractor to Electrical Inspector, "What do you mean you are going to make me follow the code?".
Register to Reply
Member

Join Date: Jul 2015
Posts: 8
#28

Re: Oxygen Concentrator Use for Nitrogen Concentration

07/23/2015 3:50 PM

Marcot, Good thought, but the desired concentration varies frequently and is even sometimes in real time as part of a sort of biofeedback system to maintain a particular patient pulse oximeter saturation level. Although a safety feature might be to order gas with the minimum O2 level that you might ever need. However, this would deplete the gas more quickly since more of the tank gas it would be used.

Register to Reply
Member

Join Date: Jul 2015
Posts: 8
#30

Re: Oxygen Concentrator Use for Nitrogen Concentration

08/04/2015 10:52 PM

I picked up an O2 concentrator. I took the cover off and plugged it in at home and quickly found the exhaust (waste) output.
I put the machine onto the anesthesia monitor. 18% oxygen was the reading of the waste gas output, approximately 5,000 ft of oxygen partial pressure. That concentration does correlate with the really large exhaust volume. That is, the 40 liters of waste N2 per minute that had to be exhausted from this 10 LPM O2 generator was being flushed with over 200 LPM of air.
Now, looking at how the machine works I can see that there is a tradeoff between efficiency (O2 concentration) and O2 volume and the controlled factor is how much the adsorbant is flushed or regenerated between cycles. In order to get a higher 02 concentration, some of the slightly contaminated (with N2) oxygen in the cylinder must be wasted in the regenerative flushing gas. That is, to get a high FiO2 in the output you must flush away some O2 that is contaiminated with N2 and use shorter waste gas flushes. An O2 generator is optimized for O2, not N2.
So, I can get to Denver, but not much higher without modification of the machine. I believe that if I alter the cycle ratios then I could get a higher fraction of N2 but I'm still just guessing that would even work. Here is an explanation of how a similar machine works for concentrating N2. For an O2 generator, just reverse the words 'oxygen' and 'nitrogen'. This excellent page was found earlier by solareagle.
http://www.nitrogen-generators.com/nitrogen-generators-how-it-works/
In addition, the optimal way to generate N2 with pressure swing adsorption is to use the correct adsorbant with the schematic shown below and this is not equivalent to using the waste nitrogen output of an O2 generator instead of the intended output. But, I'll see if I can alter the cycle times and get a change on the output. Will update. Here is a pic of the back of the machine. Note the layout is about the same as the description in the web page.

Register to Reply
Participant

Join Date: Jul 2017
Posts: 1
#31
In reply to #30

Re: Oxygen Concentrator Use for Nitrogen Concentration

07/17/2017 9:47 AM

18% O2 seems high, from my experience. A while back, I did your experiment (with an AirSep NewLife Elite) and got 12.7% (~12,000' altitude equivalent.) Assuming your anesthesia monitor measures O2% accurately, I see two probable causes of your high reading: 1) Your concentrator's oxygen flow wasn't set to its max setting. (i.e. changing O2 flow changes altitude setting.) 2) Your concentrator has degraded, possibly due to a worn compressor or contamination (e.g. moisture) in its zeolite beds. If your concentrator isn't producing 90+% pure oxygen even at its highest flow rate, it needs attention. You shouldn't have to alter the machine's cycle ratios (or anything else on it) to get 12,000' air out its exhaust port. Companies that sell O2 concentrators often service used ones.

A few things to consider:

1) I WOULDN'T use a nitrogen generator for your purpose: they can produce very pure nitrogen (99+%), which would kill you if O2 wasn't mixed in at the right ratio.

2) I WOULDN'T use nitrogen from a tank, for the same reason: if your hardware malfunctions, you're dead.

3) Oxygen concentrators, like are used for patients needing oxygen for breathing, use a different material for separating O2 from N2 than nitrogen concentrators. If oxygen concentrators degrade, they produce less-pure oxygen, which means their exhaust contains less-pure nitrogen. If the purest nitrogen from the O2 concentrator won't kill you, neither will its less-pure (because of inevitable malfunction) nitrogen.

4) While experimenting, get an oxygen monitor (e.g. from Amazon) to measure the air you intend to breath during altitude training. Spend a few days using that monitor to measure the hypoxic air, before you use your body to measure it. It also wouldn't hurt to get a pulse oximeter (also cheap from Amazon.) You could also put your generator on a timer, so it shuts off after a short time, giving you a chance to recover if experiments go awry.

5) Several companies have sprung up to supply athletes and mountain climbers with equipment and protocols to enable them to acclimate to altitude while living at sea level. They supply hypoxic air generators (essentially rebranded O2 concentrators), as well as tents (as a place to breathe high-altitude air), masks (breath high-altitude air while exercising), O2 monitors and even air conditioners to keep tents comfortable. Some also rent the equipment. But, not surprisingly, they must charge for their engineering/marketing services, so their prices are 3 to 4x what a smart and motivated individual (e.g. engineer :) ***could*** build the equivalent equipment for. At least several of these companies have been in business for over a decade, and since their prices aren't outrageous, I'm guessing their products are pretty safe. If their engineers can make a safe high-altitude air generator, so can other smart engineers.

Please continue to share your results!

Register to Reply
Register to Reply 31 comments
Interested in this topic? By joining CR4 you can "subscribe" to
this discussion and receive notification when new comments are added.

Comments rated to be Good Answers:

These comments received enough positive ratings to make them "good answers".

Comments rated to be "almost" Good Answers:

Check out these comments that don't yet have enough votes to be "official" good answers and, if you agree with them, rate them!
Copy to Clipboard

Users who posted comments:

Curious1 (1); dejswa (7); Ed Watts (1); horace40 (1); JavaHead (1); lyn (3); marcot (2); Mikerho (1); North of 60 (2); PWSlack (1); simonsd (1); SimpleMind (1); SolarEagle (4); tcmtech (2); Tornado (2); Wal (1)

Previous in Forum: New Outlook about Death   Next in Forum: What is This?

Advertisement