Lets say theoretically, your fancy NMR machine has quenched and the liquid nitrogen has evaporated and essentially has forced all the oxygen from the room. Would you be in distress when you walked into the room? would you even know it? would it feel like you were suffocating?
Or would you just take several steps and black out without having a clue you were in any danger?
My WAG is that you would immediately get the feeling of holding your breath for too long (suffocating).
Does nitrogen have a smell associated with it?
Nitrogen has no smell. The air you breathe right now is 80% nitrogen.
You will not get a suffocating feeling because your body is still eliminating CO2.
So, yes; you black out and die. This is a known and sadly not uncommon industrial accident. Grain silos are a particular danger.
A quench will boil the liquid Helium rather than the outer vessel of Nitrogen. But here the danger is no less real. You might notice your squeaky voice before passing out. MRI scanners and other cyrogenic magnets have external venting of the cryostat for just this reason.
Interesting question.
Nitrogen is an inert, odorless gas and comprises roughly 80% of the air we breath. So I am thinking that you would not notice until you began to get dizzy.
It would be a very pleasant way to die. You simply fall asleep with no discomfort. A technician at NASA died this way in space shuttle shortly before its first launch.
The brain cannot sense oxygen, it senses carbon dioxide. As long as you are eliminating the CO2, you feel no sense of suffocation. There is a great segment of Dr. Jonathan Miller’s series, “The Body in Question,” where he demonstrates this on himself. As the credits roll on that episode, his crew comes in with an oxygen mask to revive him. I wonder if it can be found on YouTube. It was a wonderful series.
Yeah you’d pretty much fall unconscious within a few seconds. Nitrogen is used to inert atmospheres in industrial settings. People get killed by nitrogen fairly often. We just saw a training film on it. Apparently OSHA is pushing it since there have been a few accidents with it in recent years.
Why within a few seconds? Does lacking oxygen makes you passing out so quickly? For instance, one can holds one’s breath for quite a long time. What is the difference when you’re breathing pure nitrogen instead?
The difference is there is no oxygen in your lungs.
Google “confined space”
I googled “confined space nitrogen” and got this;
http://www.efilmgroup.com/News/Confined-Space-Accident-at-Chemical-Plant.html
It is not necessary for nitrogen to displace all of the 21% of oxygen normally found in the air in order to cause harm to people. OSHA requires that oxygen levels be maintained at or above 19.5% in order to prevent injury to workers. According to the Compressed Gas Association, “exposure to atmospheres containing 8-10 percent or less oxygen will bring about unconsciousness without warning and so quickly that the individuals cannot help or protect themselves.” Exposure to an atmosphere containing 6-8 percent oxygen can be fatal in as little as 6 minutes. Exposure to an atmosphere containing 4-6 percent oxygen can result in a coma in 40 seconds and subsequent death.
Yes! I was remembering exactly this sequence when I saw the OP. The particular demonstration contains a range of important issue.
He puts of a mask that connects him to a container of air with a pair of bellows that allows him to breath in and out of the container. First time, just the container of air. As he breaths the CO2 level in the container rises, and eventually he cannot cope any longer and he hauls the mask off his face gasping. The second time they add lithium hydroxide to scrub the CO2 from the expired air. This time he has no discomfort and eventually just passes out. If he had been left, he would have died. During the demo he writes on a pad, and the writing becomes more and more disorganised and messy, as the oxygen levels in his blood drop, becoming a scribble before he passes out.
I had no clue that complete lack of oxygen in the lungs would cause immediate unconsciousness. Even though, when I think of it, if it weren’t the case, you wouldn’t loss consciousness as soon as your heart stops beating.
I also didn’t know that the feeling of suffocation came from an unability to get rid of CO2 as opposed to a lack of oxygen.
Interesting.
This is absolutely correct. And it is important, and significant.
Years ago, when I was in the Boy Scouts, one of many useful things they drilled us on was this: You see someone laying unconscious on the ground. The normal human reaction is to run in to help them. But that’s wrong. The right thing to do is to take a step or two back and assess the situation - why are they unconscious? Is there something hazardous nearby?
Of course, I’m an idiot. So I have some first-hand experiences.
The surprising thing, if you haven’t experienced it, is how fast it occurs. If you take a normal breath of non-oxygenated “air”, you black out really quickly. It’s not like holding your breath underwater - if you “think” you’re breathing normally, you exhale, losing most of your oxygen. Then you inhale, taking in no oxygen.
Both times for me came because I decided to use the terrible method of “smelling” equipment to see if it was clean. So both times I brought said equipment close to my face and inhaled deeply.
And both times, said equipment had significant amounts of volatile compounds still present.
It really is a shock. You think, “Well, I can hold my breath for over a minute!” But when you “expect” to be breathing normally, what really happens is this:
Your knees buckle, you black out for a second or two, and you crash to the ground. I was lucky both times, in that I didn’t fully collapse, and the equipment i was holding fell away from me. But lesson learned. No more using the old “nose GC.”
Nor did I.
What happens if you’re in an atmosphere that’s 20% oxygen and 80% carbon dioxide? Will the high CO2 level around you prevent you from getting rid of CO2 in your lungs and cause you to suffocate even though there’s a breathable amount of oxygen?
Even if that weren’t the case, you would still lose consciousness as soon as your heart stops beating. Loss of consciousness in the case of loss of pulse is caused by loss of blood pressure. It has nothing to do with the amount of oxygen in your lungs. Even if your lungs were full of pure oxygen, you would still pass out.
The answer isn’t simple. Haemoglobin has a higher affinity for oxygen at high temperatures and low pH, and a higher affinity for CO2 at low temps and high pH. The idea being that it preferentially grabs haemoglobin from respiring tissue and preferentially grabs oxygen from the lungs.
So even at elevated atmospheric CO2 levels, your body would still be disposing of CO2. The question is whether it would do so fast enough. I imagine that at 80% you would suffocate fast, but still more slowly than in an atmosphere with no oxygen.
The other silent points that you would feel like you were suffocating. There is no way you could accidentally suffocate in an 80% CO2 atmosphere.
In my early teens, I saw a sink with a slab of dry ice in it. The dry ice was sublimating, and it was easy to see that the CO2 vapor had filled the sink and was spilling out of the sink to the floor.
I was curious about what pure CO2 smelled like, and what the effects of breathing it would be. First I put my hand in to feel the temperature, and was surprised to find that it was not very cold at all. So then I put my head in, took a deep breath, and IMMEDIATELY got so dizzy that I nearly passed out. I did not understand why the reaction was so immediate, but I was smart enough to take some big breaths of regular air real quick. Emergency over.
Don’t try this at home. Your mileage may vary.
Many thanks to JWT Kottekoe,whose post has finally explained a lot of this to me. The brain is aware neither of oxygen nor nitrogen, but it is very aware of CO2 levels, which it is always trying to lower, and I went and put a sudden increase on it!
Doing a little online research, I found that the air we normally exhale has a CO2 level of about 4%. Normal air, which is what we inhale obviously, has a CO2 level of about .04%. I also found a cite that said that even with adequate oxygen, a CO2 level of 30% is fatal.
YMMV is apropos. In my case, we had a top opening freezer filled with dry ice to keep a plastic from catalyzing and hardening. I stuck my head in to pick up an object I dropped inside and took a whiff. Gawd! The inside of my nasal cavity felt like it was burning! You know how your nose burns when you burp up the CO2 from a bottle of soda? It’s much, much worse…think of it as a gaseous water boarding.
Are there any sensors that can detect a dangerously low oxygen level, that could be hooked to an alarm in places that use liquid nitrogen?
Where I worked for many years in the petrochemical industry there was a case where nitrogen (N2) was being used for fresh air instead air. The welder was working inside a pipe. When the welder was found he had blacked out. He lived but was a vegetable.
Someone had accidentally hooked up a hose to a N2 connection instead of the air connection.
Also another case of workers inside a large vessel. Rusting material inside the vessel was eating up the available oxygen (O2). The workers began to have headaches. Safety was called to check the O2 level and found it was dangerously low. Fresh air was then added to the vessel so workers could work safely.
We had portable O2 meters and meters that showed % combustibles in the air.
There are little lapel pins with LCD displays showing % O2 and a buzzer that goes off when it drops below a set percentage. These are mandatory when working around walk-in temperature chambers that use dry N2 to keep the H2O moisture content as close to zero as possible.
ETA–I see olefin32 beat me to it.