Hydrogen doesn't have any toxic effects that I'm aware of, and none is shown in the available literature. The atmosphere would be 33% oxygen, which is substantially higher than the 21% that we're used to. Now, an oxygen concentration that's too high can have negative health consequences over time, but I don't think 33% would be especially harmful, especially in the short term. (Actually, in space, you could maintain that environment at two-thirds of normal pressure, which would make the oxygen concentration you get just about spot-on).

So, you could survive in that atmosphere more or less indefinitely. Now, if a person was breathing that atmosphere, it wouldn't stay at that concentration. The O2 would lower and (more urgently) the CO2 levels would rise. The simplest way to deal with that is to keep producing more H2 and O2, and venting the old stuff out, but that would be limited by the supply of water and of power you have (splitting water in large quantities takes a whole lot of power).

Of course, the problem with this is that you're basically living inside a very delicate bomb. It's a chemically perfect environment for ignition with very low ignition energy. That means that a single static spark from your clothes or from touching the wrong pieces of metal together, or there's an electrical contact or two pieces of metal hitting or rubbing, and the whole thing goes up. The entire room would immediately turn into a massive fireball, totally incinerating anything inside, and probably blowing out the walls. There's a lot of energy in H2 and O2 and it doesn't take much to liberate it all.

Incidentally, while I write this, it occurs to me to wonder about the presence of moisture. If everything is wet, it makes a static spark less likely, but it makes an electrical short more likely. If there are any exposed wires, switches, plugs or other contacts in the room, you'd want to keep it bone-dry, but if everything is dry, it's very had to prevent static buildup. Either way, I wouldn't want to be in that room for very long, because sooner or later a fireball is inevitable.

IF the elctrolysis was done without problems (i. e. no chlorine or excess ozone in the room) then the resulting mixture of 1/3 oxygen and 2/3 hydrogen is safe to breathe at least for some minutes.

Oxygen at 1/3 atmosphere and normal pressure is okay, even longtime, and hydrogen is not toxic either.

Of course, one should not even THINK about smoking in this room ;-(

Hindenburg disaster - Wikipedia

Yes, in principle, but read on…

Electrolysis has been used for many years to provide oxygen on submarines.

All that’s required is the proper equipment and an energy supply and designed to produce the required amount of O2.

We can easily calculate the amount of water and power required with a little information:

• The average human adult requires 550 liters of O2 per day at Standard Temperature Pressure (STP).
• O2 has a density of 1.429 g/liter, or 0.001429 kg/liter.
• Electrolysis requires about 6.25 kWh of energy per kg of O2 produced from water.

So, first we obtain the O2 per person/day in kg:

550 liters/day/person * 0.001429 kg/liter = 0.78595 kg/day/person

(Round this to 0.786 for convenience.)

Next, the power requirement can be calculated:

0.786 kg/person/day * 6.25 kWh/day/kg = 4.9125 kWh/person/day

The final step is to divide the kWh power per day by 24 hours to get to the average (continuous) power level required for the electrolyzer:

4.9125 kWh/day/person / 24 hours/day = 0.205 kW/person,
or 205 Watts/person continuous power.

Where would that energy come from? For example, if we consider using solar panels, we’d need to have enough so that they can produce the needed oxygen during sunlit hours.

A generally reasonable and handy rule of thumb is that each square meter of solar panel produces about 0.72 kWh per 24-hr daily cycle.

From this, we can calculate the solar panel requirements per person:

Solar panel area = 4.9125 kWh/person/day / (0.72 kWh/day/m^2)
= 6.23 m^2/person

Now, this simplistic approach would work if the solar panels were connected directly to the electrolyzer, but there would be a problem. This is that the Oxygen levels would vary, rising to a peak at the end of the day and then falling at night, reaching the lowest level just at sunrise. This might work out if the human(s) are active (and using more O2) during the day and inactive during the night, but can we count on that?

Instead, we’d want to operate the electrolyzer with a control system and an O2 sensor (like a thermostat on an A/C system), to keep the O2 within a tight range. This would require that the electrolyzer operate on demand, and this, in turn, means that power would be needed at night. Therefore, we’d need to have a means of storing the solar energy collected in a battery system.

As an alternative to using batteries, the system could produce O2 during daylight hours and store it in tanks, with a system to control the release of the O2 at the proper level.

But there is yet another problem. Carbon Dioxide (CO2) is formed as the byproduct of human respiration. If we simply keep making more O2 from water, at some point the pressure in the house would rise due to the overall introduction of mass in the form of O2 and CO2. We could simply vent to the outside to keep the pressure equal, but this would ultimately result in an internal atmosphere of O2 and CO2, which is profoundly different than the normal mixture of atmospheric gases, which is 78% N2, 21% O2, 0.98% argon, and traces of other gases, down to CO2 at 0.038%.

Assuming the system is closed, then it is imperative that the CO2 be somehow removed. This is done by various processes, but also requires a source of energy.

So, as you can see, the answer to your question at first seems simple and straightforward, but supporting humans for a long period of time in a closed environment requires careful analysis and planning. That is the art of those who design and operate life support systems on board submarines, the International Space Station, and someday soon, on interplanetary voyages.

The in-depth answer is (as usual) in Wikipedia.

The short answer: You can, but don’t do it for more than a day.

The medium answer: Oxygen is a reactive gas. That’s good for us; we breathe it, and it reacts with our food to keep us alive. We have mechanisms at the cellular level - antioxidants such as glutathione - to make sure that we don’t get messed up by its reactivity. If you breathe too much oxygen, you overwhelm these mechanisms, and your cells start getting damaged by reactive oxygen species. Whether it’s pure or not is irrelevant - it’s how much you’re breathing.

Down here on Earth, we breathe 21% oxygen at 1 atmosphere. Anything up to about 50% is OK, and there’s enough slack in the system that our cells can handle that.

If you’re in space, you might breathe 100% oxygen at 0.2 atmospheres. That’s the same amount of oxygen per breath, so that’s OK. It’s pure oxygen, sure, but you’re not getting too much of it, and that’s the key thing.

You can breathe 100% oxygen at 1 atmosphere for a couple of hours, as one respondent said, and you’ll be absolutely fine. Your cells have glutathione to spare. Just don’t do it for too long. Your lungs will be the first to suffer, and you can measure decreased lung function after 24 hours. Some people react quicker, some might be OK for 48 hours before their lungs start packing up.

Electrolysis of water can be used to produce as much oxygen as you want, limited only by the supply of water, the supply of electricity, and the equipment you have available. The amount of water you’d consume to provide yourself with breathing air is pretty trivial

There are a bunch of problems with doing that in real life, though. The simplest is that electrolysis is a big energy hog. Your household electric grid might be able to handle it (depending on how efficiently you can run the electrolysis), but it would use a lot of power. The second problem is that electrolysis tends to be a pretty harsh service, so designing a system that isn’t going to corrode itself as it operations, or create a bunch of other undesirable byproducts would be a challenge.

But let’s say you do all that (which isn’t impossible), you could, then have a household electrolysis unit that puts out a constant supply of oxygen. It also puts out a constantly supply of hydrogen. You’d better vent that outside, so it doesn’t build up to flammable levels and consume you in a fireball.

But even if you do that, providing oxygen is only half the battle. You’re still breathing out CO2 every time you exhale. CO2 will eventually build up to toxic levels. In fact, when someone suffocates, it’s usually the CO2 accumulation that kills them before the lack of O2. If you try to get ride of the CO2 by venting it outside, then you’d have to produce enough O2 to displace all the air in the house, which would result in a pure oxygen environment, which would both be harmful to you, and would mean that your whole house would burn down with the first spark (even most metals will burn in pure oxygen).

Now, none of this is impossible to work around. Both submarines and spacecraft have been designed to use electrolysis, along with CO2 scrubbers and various methods to get rid of hydrogen. It’s a thing that can be done. But it requires a lot of equipment and engineering to pull it off.

Sure, once.

Your system is designed for 21% oxygen. Of course you can breathe “air” with more or less O2, even 100% O2 (but you shouldn’t for long unless your lungs are really compromised).

Careful with H2 and O2. You don’t want to float off. — kidding. But seriously, that ratio of H2 and O2 is the stoichiometric ratio that will produce a really big bang if ignited. You would want to avoid sparks or open flames when dealing with such a mixture. Breathing it is probably not the smartest thing to do in life.

2H2(g) + O2(g) → 2H2O(g)

During the electrolysis of water, oxygen gas is released through a chemical process that involves breaking down water (H₂O) into its constituent gases, hydrogen (H₂) and oxygen (O₂). Here's a step-by-step explanation of how this occurs:

### **1. Electrolysis Setup**

In the electrolysis of water, an electric current is passed through water that contains an electrolyte (such as sodium sulfate or potassium hydroxide) to enhance conductivity. The setup typically consists of two electrodes—an anode (positive electrode) and a cathode (negative electrode)—immersed in the water.

### **2. Electrochemical Reactions**

When the electric current is applied, two key reactions occur at the electrodes:

- **At the Anode (Oxidation Reaction):**

- Water molecules lose electrons (oxidation), resulting in the production of oxygen gas and hydrogen ions (protons). The half-reaction at the anode is:

\[

2 \text{H}_2\text{O} \rightarrow \text{O}_2 + 4 \text{H}^+ + 4 \text{e}^-

\]

- This reaction generates oxygen gas (O₂), which bubbles up at the anode.

- **At the Cathode (Reduction Reaction):**

- Hydrogen ions (protons) gain electrons (reduction) to form hydrogen gas. The half-reaction at the cathode is:

\[

4 \text{H}^+ + 4 \text{e}^- \rightarrow 2 \text{H}_2

\]

- This reaction produces hydrogen gas (H₂), which bubbles up at the cathode.

### **3. Overall Reaction**

The overall chemical reaction for the electrolysis of water can be summarized as:

\[

2 \text{H}_2\text{O} \rightarrow 2 \text{H}_2 + \text{O}_2

\]

This equation shows that for every two molecules of water, two molecules of hydrogen gas and one molecule of oxygen gas are produced.

### **4. Collection of Gases**

The oxygen gas produced at the anode and the hydrogen gas produced at the cathode are collected separately. In a typical electrolysis apparatus, gases are captured in separate containers or tubes attached to each electrode.

### **Summary**

During the electrolysis of water, oxygen gas is released as a result of the oxidation reaction at the anode, where water is split into oxygen gas, hydrogen ions, and electrons. This process is driven by the electric current passing through the water, which facilitates the breakdown of water molecules into their elemental gases.

No.

You see, the whole point of breathing oxygen is to get rid of 4 H+ atoms by making them react with 2 electrons and an O2 molecule. In the process, the mitochondrion creates a H+ gradient that then leverages to synthetize ATP, the cell’s energy-carrying molecule.

So, the mitochondrion makes water out of oxygen and hydrogen, and gets energy in exchange

Electrolysis is exactly the opposite of respiration.

You take water, spend energy into breaking it and end up with oxygen and hydrogen.

So no, fish don’t do electrolysis of water because that consumes the same amount of energy that the produced oxygen would give them (well, accounting to imperfect yields, they would lose energy).

It’s like selling your food at a loss in order to buy food. You will end up with no money and no food in no time.

If cells can get the energy necessary for electrolysis of water… they won’t use it for that! They’ll use it instead of consuming oxygen, if oxygen is not available.
But in any case, fish can’t do that.

Yes. Normal room air is 21% oxygen, we absorb about 4% (varies depending on health and activity). So we exhale a breath with about 17% oxygen. The danger comes from excessive carbon dioxide inhalation. Our central chemo receptors detect our CO2 levels and adjust our respiratory rate. Body likes a ph 7.35–7.45 and CO2 level 35–45. Too much or too little CO2 and the body needs to adjust. If you’re hyperventilating/blowing off to much CO2 then you pass out, to reduce respiratory rate and thereby reduce CO2 loss. Retain too much and guess what, you pass out again. This time your respiratory rate slows not to retain CO2 but to allow for more CO2 to be exhaled because CO2 intoxication leads to full blown arrest. What an amazing and complicated process living is!

No, they’re elements. You were able to electrolyse water into hydrogen and oxygen because the binding energy between atoms is weak enough to break that way, but the binding energy inside an atom is much, much stronger. If you want to break oxygen down you have to get really creative, and if you want to break hydrogen down you are really out of luck, because it is already as simple as matter gets.

One slight disclaimer: it’s possible to split a molecule of either of them down to single atoms, but they’re very reactive that way and don’t stay single atoms for long. (That’s part of the reason gunpowder goes bang: there’s a reaction there that frees up atomic oxygen, and that takes the high reactivity of molecular oxygen and turns it up to 11.)

Extracting from the air is almost certainly the more feasible method.

I’m fairly sure that almost all medical oxygen, and most likely also oxygen used for industrial purposes such as gas welding comes from use of oxygen concentrators, which operate based on the size difference between oxygen and nitrogen gas molecules.

This commercial website shows a more complex system, but using the same overall concept of pressure swing adsorption.

In the old days, the method was to distill it from liquid air, which I’m fairly sure is still preferable to electrolysis of water from an energy standpoint, although I haven’t done the maths to figure out how much energy is needed to make liquid air and then boiling off the nitrogen from that by keeping the air at just over -195 C (boiling point of nitrogen), but below -183 C, the boiling point of oxygen.

Getting it from air is much cheaper and simpler. Cool the air down to liquefy it, boil off the nitrogen (recovering it’s “coldness”), and there you are - liquid oxygen*. About 5 to 10 cents a pound in ton quantities. Oxygen from electrolysis costs about 35 cents a pound just for the energy costs. Now electrolysis also produces hydrogen, with which you could run a fuel cell to generate some of that electricity, but that’s an awfully roundabout way of doing it. The plant is much bigger and more expensive to build and run - and you’d still need to supply energy to liquefy the oxygen produced.

Lastly, no, you cannot get enough electricity out of the hydrogen produced to supply all the electricity needed for the electrolysis, in spite of the occasional patent and claims on the web. Perpetual motion isn’t a real thing

*Yes, there’s a percent of argon left, but that can be separated too.

If you use it for hobby and if it is not strictly necessary that obtaining pure hydrogen, you can use solubulity difference of hydrogen and oxygen. In 20 Celcius oxygen is 27 times more soluble than hydrogen so after electrolysis you can pass through your gaseous mixture into pure water, if you do it 2–3 times you obtain high percentage of hydrogen in gas mixture.

Since oxygen solubulity in water is finite, this method is not fot long term production. You can heat the water(that oxygen solved) to clear(dissolve oxygen) them and use again.

*solubulity of gasses in water is inversely proportional to temperature.

I just leave it to my autonomic nervous system, mostly. Every now and again, the build up of CO2 in my lungs gives me the urge to inhale voluntarily. Upon filling my lungs from the atmosphere, my lungs use a thin and high area tissue to expose the red blood cells in the capillaries to the oxygen present, and this changes the hemoglobin to oxyhemoglobin, which is carried away to release the oxygen into my bodies cells. The CO2 moves out into the air sacs and is exhaled as I breath out. This usually provides relief for a short time, but the build up will make me repeat the process.

There is only 20.5% oxygen in the atmosphere at best though. It is regarded as a bad thing to breathe in higher concentrations, unless you have good reason.

Inhale just means breath in, of course. How much you absorb is a different issue.

When you do electrolysis, the electric current first breaks the water molecule into hydrogen and oxygen ions. The hydrogen ions are negative and as a result get attracted to the positive end (cathode) of your electrolysis circuit. The oxygen ions are positive and get attracted to the anode.

Only once large numbers of these ions gather together near either the cathode or anode to the combine together to make hydrogen and oxygen molecules.

As a result you do not need any special material to separate the hydrogen and oxygen. You just need to separate your anode and cathode physically in space, to collect each product gas around that particular electrode.

The oxygen gas come from a negative ion O2- will be attracted to the anode of the power supply. You can collect the gas there through the water displacement method.

Water (H20 )by Electrolysis process 2 hydrogen & 1 Oxygen can produce gas but take care useing water quality may affect O2 gas quality ( avoid chlorinated water , chlorinated water may produce toxic chlorine gas together with o2 gas, if breath chlorine gas its toxic ) also H2 gas should properly vent out from closed room ( h2 gas is highly flamable , may fire & explosion in closed room) , so with out tech study dont use ,

Hydrgen gas production method is Electrolysis process & Oxygen gas production is very less compared with Hydrogen production , so oxygen production is unecconimcal in electrolysis .

Medical Oxygen gas purity , impurities must be checked , certified & recorded as per GMP.