Back at the start of the pandemic, a variety of hacker designs for life-saving machinery may have pushed the boundaries of patient safety. There are good reasons that a ventilator must pass extensive safety testing and certification before it can be attached to a patient, because were it to in some way fail, the patient would die. A year later, we have many much safer and more realistic ways to use our skills as part of the effort.
Probably one of the most ambitious projects comes from a coalition of Indian hackerspaces who are adapting a proven oxygen concentrator for local manufacture. Among them is Hackaday’s own [Anool Mahidharia], who hosts a Maker’s Asylum video (embedded below) explaining how the oxygen concentrator works and how they can be made safely.
An oxygen concentrator is both surprisingly simple and imbued with a touch of magic. At its center are two columns of zeolite, a highly porous aluminosilicate mineral that performs the task of a molecular sieve. When air is pumped into the column, the zeolite traps nitrogen, leaving the oxygen-enriched remnant to be supplied onwards. There are two such columns to allow each to be on an alternate cycle of enrichment or purging to remove the accumulated nitrogen.
The point of the video is to show that such a device can be constructed from readily available parts and with common tools; as the title says it isn’t rocket science. Concentrators produced by the hackerspace coalition won’t save the world on their own, but as a part of the combined effort they can provide a useful and reliable source of oxygen that will make a significant difference in a country whose oxygen distribution network is under severe strain.
We previously covered the Indian oxygen concentrator effort when they launched the project. Their website can be found on the Maker’s Asylum website, and their crowdfunding campaign can be found on the Indian crowdfunding platform, Ketto. They have already proved their ability to coordinate large-scale manufacturing with their previous PPE and respirator projects, so please consider supporting them if you can. Meanwhile, we can’t help a twinge of space envy, from the fleeting glimpse of Maker’s Asylum in the video.
Nitrogen? Surely you mean hydrogen, no?
No. Air is largely nitrogen. To oversimplify, this acts to filter out nitrogen and allow oxygen to pass. Hydrogen would ALSO pass through, but there isn’t really much free hydrogen down here.
Ummm yeah sorry my mistake, mixed it up with water didn’t I. Oops
Look up the chemical composition of ‘air’, that will answer your question pretty quickly.
Why would he mean “hydrogen”?
Nitrogen makes up ~79% of the atmosphere, oxygen ~20%
Probably thinking of filtering H from Browns gas after electrolysing H2O. Which is what I was expecting them to be doing.
Had no idea you can filter Nitrogen like that!
Maybe?
I used to condense oxygen to play with when I worked with cryogenics (specifically liquid nitrogen) – it’s a blast :)
Thanks for the brilliant video. It would be great to have a parts list and some written more detailed instructions. Thanks.
On the Git repo at
https://github.com/MakersAsylumIndia/M19_OxiKit
and more info at OxiKit.com
In all that information after all i dont get, what sort of ceolite is used in that designs. big group of materials is named ceolites – syntetic or natural, various forms of granulas, various size of micropore and many parameters
We’re using Sodium 13x , 0.4-0.8 mm granule size
But you can also use Sodium 5A or LithiumX
( process parameters may need more tuning)
5A is a Calcium A zeolite. The Sodium version is 4A.
LiX is of course the best material but will cost you 4-5 times.
All of them need to be handled carefully with respoect of picking any moisture while loading.
Dead link for the “Maker’s Asylum.”
https://www.makersasylum.com/m-19-initiative-makers-vs-covid19/
Correct (or at least functional) link:
https://www.makersasylum.com/m19-initiative/
Thanks, link is now updated in the article.
ACS Materials says that type of Zeolite that is optimized for this type of use is 13X (https://www.acsmaterial.com/blog-detail/type-a-and-x-zeolites.html). 10 Angstrom sieve. The Oxikit website (https://oxikit.com/) only mentions zeolite – which is material 230+ types wide.
I’ve 3 O2 concentrators for home use. Two are bad from high humidity I believe. I’ve tried recovering the zeolite using a vacuum chamber and a 400°C hot plate. Every attempt and reloading of zeolite results in reduced O2% output. I suspect I might need a 1000° C muffle furnace. I wonder if the zeolite in the sieve tubes goes bad progressively from input downward and if mixing it to cook makes it worse. Advice would be appreciated. Thanks.
Could be a bunch of other factors. You haven’t mentioned which specific zeolite your concentrators have.
* Tightly packing the zeolite is important, so if you are losing some amount of zeolite during the recovery process, you may have to “top up”
* Check for leaks. A liquid soap test helps find leaks.
* Look for degraded compressor performance.
Thanks for the reply and advice:
* Tightly packing the zeolite is important, so if you are losing some amount of zeolite during the recovery process, you may have to “top up”
Two of the concentrators are the 0-7L Home O2 concentrators sold on ebay. When I cook and subject the zeolite to vacuum it seems to change from a light brown to a light gray. My degassing tank imploded when its top slipped and some was lost when working with a failed portable. Some I brushed up is sitting here and has not reverted to the darker color. I can put it in my palm, add water, and it doesn’t warm.
* Check for leaks. A liquid soap test helps find leaks.
I use a hand vacuum pump to draw a vacuum on the sieve tubes and watch for a loss of pressure. They test good when closed. On the failed portable it looks like they left out O rings to lower drain on the battery. I barely get a 1% increase in O2 but then I don’t think I ever got better than a 30% at the faceplate output. When I insert my O2 meter in directly after the sieves I seemed to get higher than a low 30% but later found that the O2 meter gives erroneously high readings if its inserted and output port sees higher than normal pressure. I will try liquid soap.
* Look for degraded compressor performance.
Seems good. Did a pressure test and hoses popped off.
No exothermic reaction – not heated enough?
Who proof reads these?
I think you mean “Who proofreads these?” and if you mean these comments, we proofread each other!
How do they measure the O2 percentage?
@Jan Praegert said: “How do they measure the O2 percentage?”
I was wondering the same thing, so I did some digging…
Beware, depending on the type some oxygen concentration sensors last 5 years, some only 12 – 18 months. Also, some O2 concentration sensors require a continuous gas flow.
The sensor [1] below is a “Galvanic Type Micro Fuel Cell”. It measures 0% – 100% +/-1% O2 concentration, has a 5 year lifespan, and costs USD $55.00. The output is linear 10 – 15.5 mV, so an instrumentation amplifier is called for.
Optical O2 concentration sensors are quite interesting, see [2] below & download the datasheet. But the optical sensors seem to only measure 0% – 25% O2 concentration which which is OK for Earth’s ambient atmosphere, but not for concentrated O2.
Automobile sensors might work but they can get expensive, $40.00 – $150.00+, finding a datasheet is difficult, and there are at-least several types: a “broadband” type which seems to analyze input fuel-air mixture, and at least two exhaust “narrowband” O2 sensors, one “upstream” of the catalytic converter and one “downstream of the converter. Evidently one of the two exhaust sensors needs to be heated. See [3] below for how to use a common automobile oxygen sensor with an Arduino.
Link [4] is a $100 hand held oxygen gas concentration meter on Amazon. It has three ranges, 0-100%, 0-25%, and 0-5%. It is obviously Chinese, and the reviews are mixed.
Link [5] is selling the plans and BOM on “How to Build a $100 Pressure Pot for Testing Oxygen Sensors”, $12.00. It looks legit, the company sells a lot of other oxygen measurement stuff as well. Maybe what they are doing targets technical diving, rebreathers and/or exotic gas mixtures.
Air/oxygen gas mass flow and gas concentration meters exist for testing medical oxygen concentrators, but they are not cheap. See the examples at [6] which range from $1,295.00 to $1,895.00.
Well, that’s all I have time for tonight. This subject turned out to be a rather deep and twisty rabbit hole. I had fun.
* References:
1. AST SRX-25F3 …. % Oxygen Sensor, $55.00
https://www.oxycheq.com/collections/industrial-oxygen-sensors/products/ast-srx-25f3-oxygen-sensor
2. LuminOx Flow-through Optical Oxygen Sensor
https://sstsensing.com/product/luminox-flow-optical-oxygen-sensor/
3. How to use KE-25 (automobile) Oxygen Sensor with arduino
https://miliohm.com/how-to-use-ke-25-oxygen-sensor-with-arduino/
4. Gerneric CY-12C Portable Oxygen Concentration Content Tester Meter Detector (Instructions are in English Now) 4.0 out of 5 stars 14 ratings $100.00
https://www.amazon.com/Portable-Concentration-Content-Detector-Instructions/dp/B01A6JYD0M
5. How to Build a $100 Pressure Pot for Testing Oxygen Sensors (plans & BOM), $12.00
https://www.oxycheq.com/collections/industrial-oxygen-sensors/products/how-to-build-a-100-pressure-pot-for-testing-oxygen-sensors-1
6. Air / oxygen gas mass flow and gas concentration meters.
https://www.tsi.com/solutions/solutions-by-application/oxygen-concentrator-testing/
7. OxyCheq Products
https://www.oxycheq.com/collections
8. https://www.instructables.com/Easy-To-Build-Oxygen-Analyzer-Using-An-Arduino-Com/
@Drone, i have bookemarked this page, just for your roundup of O2 sensors. Thanks for sharing!
It’s not rocket science when you get your hands on a working kit from somewhere.
I saw one at the curb last week, the cover was loose. I picked it up but haven’t looked at it yet. I already have one that I replaced a bearing that shed it’s balls to the bottom of the case. It hummed and that’s all. A new bearing and it’s good.
The diaphragm compressor in these goes to 40 PSI, good enough to spray paint with or blow out things.
Of course it it isn’t. We made the first one in thr 70’s (Union Carbide/Bendix).
But as a supplier of the molecular sieve that separate the oxygen and nitrogen I am agraid getting the concentrator alone without the zeolite will be of limited use.
Another use for an oxygen concentrator is to run a torch connected to a natural gas pipe. People who make those glass animals love it because their torch never runs out, they never have to take gas and oxygen bottles in to exchange.
Dunno if an oxygen concentrator could supply enough to use with acetylene for cutting and welding steel. Now how about hacking an acetylene generator that uses calcium carbide and water, without exploding? Then we’d need DIY calcium carbide. Used to be a scrapyard near me that refilled acetylene bottles using a huge antique acetylene generator.
Must be some quite tricky business in refilling those because the acetylene has to be dissolved in something (usually acetone) in order to have enough in a bottle to make it worth while. Pure acetylene has the annoying property of wanting to spontaneously explode if compressed to more that 15 PSI, which is why when using it one must never adjust the regulator over 15 PSI, or as my Jr. High shop teacher said ages ago “Turn it right, you’re all right. Turn it left, there’s nothing left.”
I still don’t get why splitting water (Hydrolysis/Electrolysis) for oxygen is not being discussed during these (hopefully temporary) trying times.
It requires a LOT of energy, if the water’s not quite pure you get other stuff in your gas stream than just oxygen and hydrogen (like chlorides -> chlorine gas), and the process is erosive to the electrodes so you have to keep replacing them. In contrast, zeolite absorption setups can run for thousands of hours with little maintenance and much lower energy requirements.
Electrolysis is only useful, if you want elemental hydrogen. There is already enough elemental oxygen around us.
Can it be modified to trap CO2?
Do you want to replace Sodastream cylinders? It’s probably not worth it. There is so little CO2 in the air. In some greenhouses they even burnt natural gas only to get more CO2 for the plants.
As I recall, systems similar to SCUBA – only “Re-breathers” scrub CO2 from normal breathing, quickly enough so that you can continuously use it under water, no bubbles produced – they used them during WWII apparently along with other gases to sneak up on enemy ports. At issue was that when you go deeper than 20 ft it stops filtering and creates lethal CO2 poisoning. I’m sure that has changed, but I know they use them in many applications today outside of diving where enclosed breathing is required – like industrial settings where poisonous gases are present, etc.
actually, ventilators were very effcient at killing people, with a death rate between 50 and 90%.
thats why they are rarely used now. what a monumental waste of money and resources.
As someone who had his son’s life saved by ventilators multiple times during his battle with cancer I have to disagree with your narrow-minded assessment.
He lost the battle but his death wasn’t caused by a ventilator.
It’s not “narrow-minded”, at issue in the medical environment is that by the time you get put on a ventilator you are already in critical condition or close, so the survival rate is fairly low relatively speaking. Especially when you consider how fast People die from pneumonia or related illnesses that themselves kill in a short time.
You also have an issue with infection anytime you use endotracheal tube during intubation, which is what you are trying to avoid to begin with. It is a semi-last resort type of thing. Done correctly and managed it can save a life, unmanaged it can be dangerous. So in a Hospital environment where Nurses don’t stay on top of it because they are handling other emergencies, bad things can happen.
I’m sorry to hear your Son passed, nobody should outlive their children. RIP
Most automobile Oxygen sensors are NOT scalable designs. They use Zirconium and act as a ‘switch’. If there is no ‘free’ oxygen they output a voltage, if there is ‘free’ oxygen they output zero volts (ground). That makes them good for finding stoichiometric. They do require heat (supplied by the exhaust temperature in an exhaust stream). Voltage is typical a little less than 1.0 volt (0.9 or so).
I appreciate the creativity and knowledge sharing in the video. It’s a fun hands-on protect, but I’m not sure if I’d use such DIY projects in life threatening conditions. Building something that works reliably every time is a much harder problem. You all are still creating spark of creativity and that’s great.
has anyone thought about building one that would run on battery power and electric sort of like a portable but a stationary home unit