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Oxygen concentrator & Airway Gas Monitor calibration mixture

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klugesmith

Thu Jul 23 2015, 09:03PM

Registered Member #2099 Joined: Wed Apr 29 2009, 12:22AM
Location: Los Altos, California
Posts: 1714

Please excuse the double subject.

I got a portable oxygen concentrator at a local industrial auction. It's a home medical appliance, I think based on Pressure Swing Adsorption cycles. Not unlike what IAmSmooth (?) made for his nitrogen liquefier apparatus. DIY glassworkers say that O2 concentrators can deliver gas at enough pressure for a torch flame.

The PSA material eventually goes bad, so I want to measure the O2 concentration in the machine's outlet gas. Any ideas for quantitative assay using household chemicals? After the glowing-splint-in-jar-of-gas test, of course.

The auction lot also included a small centrifuge and half-a-dozen small tanks of gas mixture for "calibrating Airway Gas Monitors". What's an AGM? Any guesses as to the subjective effects of inhaling the gas?

Ash Small

Fri Jul 24 2015, 10:21AM

Registered Member #3414 Joined: Sun Nov 14 2010, 05:05PM
Location: UK
Posts: 4245

These have two chambers containing a nitrogen absorbing zeolite. They usually work on around a 22 second cycle. Air is passed through one chamber for ~20 seconds, then through the other one, nitrogen is absorbed by the zeolites. During the 'off' cycle, some of the 'enriched' gas is used to 'flush out' the nitrogen from the first chamber, etc.

These do not supply 'pure oxygen', only 'oxygen enriched air'. There 'enrichment factor' depends on the machine. The cheap Chinese ones for sale new on Ebay aren't much use.

The medical ones used here can supply up to ~ three litres per minute. They are sometimes paralleled for greater flow.

I know the zeolites last several years at least. I do know someone who tests and services these machines, but don't see him very often.

EDIT: I don't think I's want to breathe that calibration gas, Wikipedia says this about Enflurane: "Clinically, enflurane produces a dose-related depression of myocardial contractility with an associated decrease in myocardial oxygen consumption. Between 2% and 5% of the inhaled dose is oxidised in the liver, producing fluoride ions and difluoromethoxy-difluoroacetic acid. This is significantly higher than the metabolism of its structural isomer isoflurane.

Enflurane also lowers the threshold for seizures, and should especially not be used on people with epilepsy. It is also known to cause malignant hyperthermia.

It relaxes the uterus in pregnant women.

Enflurane and methoxyflurane have a nephrotoxic effect and cause acute renal failure, usually by its nephrotoxic metabolite."

Bored Chemist

Sat Jul 25 2015, 09:45PM

Registered Member #193 Joined: Fri Feb 17 2006, 07:04AM
Location: sheffield
Posts: 1022

The web says lots of things about enflurane.
The gas bottle says that it doesn't contain enflurane; it contains chlorodifluoromethane instead.

This might help

IamSmooth

Wed Aug 12 2015, 01:36AM

Registered Member #190 Joined: Fri Feb 17 2006, 12:00AM
Location:
Posts: 1567

I'm an anesthesiologist and Enflurane is a seldom used potent inhalational anesthetic. I would be extremely careful, and I suggest you get rid of it. The fumes in an enclosed space can cause loss of consciousness and loss of airway tone. This means if you go to sleep you could have your tongue obstruct your airway and die.

I am not sure if that container contains this liquid. However, whatever else is in there is better left alone. It's not worth dealing with.

klugesmith

Wed Aug 12 2015, 08:53PM

Registered Member #2099 Joined: Wed Apr 29 2009, 12:22AM
Location: Los Altos, California
Posts: 1714

Thanks for the warnings. Not something to casually inhale on purpose.

It would be interesting to determine if the 3.0% component really is chlorodifluoromethane (R-22), as some of us noticed on the label. Could see if anything condenses inside a glass tube at simple freezing-bath temperatures. BP's of R-22 and enflurane are -41 and +57 degrees C, respectively, but I can't find vapor pressures for enflurane below 20 degrees C.

Even the relatively nontoxic R-22 has IDLH (Immediately Dangerous to Life or Health) values given as 50,000 or 59,000 ppm. Its occupational exposure TLV is 1000 ppm (reached e.g. if entire contents of pictured gas bottle were diluted in 0.75 cubic meter of air). Corresponding TLV for enflurane is 75 ppm, and I found procedures for measuring it at 1 ppm (as might be found in a 1970's operating room?)

I think most teenagers who die from huffing refrigerants to get a readily-accessible buzz, didn't consider they might pass out with lungs still full of an asphyxiant much denser than air. In videos where teachers demonstrate SF6 voice (the inverse of helium voice), they make a big point of then draining the lungs & bringing in air.

I bet a jar full of gas from pictured bottle, mostly O2 and N2O, would re-light a glowing splint or make a birthday candle burn intensely. While the chloro fluoro component, whatever it is, transforms into much nastier stuff.

Enceladus

Sun Feb 19 2017, 04:59AM

Registered Member #61428 Joined: Sat Jan 14 2017, 12:39PM
Location:
Posts: 50

If you have an oxy-fuel heating torch head and two flow meters you can see what the proportions are for various flame types. Try to see how hot you can get your flame with various fuels.

If you have a precision scale you can determine the specific gravity of the product gas mixture, and from that, calculate the oxygen concentration.

Conundrum

Fri Apr 21 2017, 08:04AM

Registered Member #96 Joined: Thu Feb 09 2006, 05:37PM
Location: CI, Earth
Posts: 4059

MAP sensor from car?
I have one here, soon-too-be-removed from my i10 but it still works at least somewhat.

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