Is Nitrogen Clean gas

Nitrogen is inert.

good call. I stand corrected.

Almost right. It is true that CO2 is a trigger to breathing more deeply. It is not true that breathing nitrogen (or any other inert gas) lowers the blood CO2 partial pressure. The partial pressure remains the same, and one carries on breathing the hypoxic mixture in an apparently normal fashion until one passes out from the lack of oxygen. The receptors controlling breathing in humans, unlike the ones in rabbits, do not normally have a sensitivity to low oxygen levels.

It is not true that breathing nitrogen (or any other inert gas) lowers the blood CO2 partial pressure.

I am no expert, but the person writing in the link I provided has a degree in medicine, as well as physics, and was describing a personal experience. So I believed him.

Do you have a link to a source that supports your comment? I would be very interested to see it.

Interesting case. But I think your inference is not quite right. By the reasoning described by the author, his CO2 levels were low because he had hyperventilated/ 'superexhaled' the CO2 which we produce all the time and have to get rid of (the trigger to breathe based on the necessity to get rid of CO2 waste). Would breathing in Nitrogen actually lower your CO2 level? Maybe not unless it also caused you to hyperventilate....

Good point about the hyperventilation.

I can't find anything that quantifies the blood pCO₂ changes when you breath something like nitrogen. But there is a lot of mention of a lack of the high pCO₂ being a reason for nitrogen asphyxiation to be free of the 'gasping for air' effect.

Yes. The gasping effect is produced by the reflex of the body trying to exhale and get rid of CO2 to no avail. In case of nitrogen asphyxiation, CO2 is exhaled normally, so there is no distress reflex. However since no oxygen is breathed back in, loss of consciousness and death result in minutes. This can happen pretty much without warning, and it does make N2 a hazardous material to use in confined spaces.

"Nitrogen narcosis" is similar but caused by dissolution of the gas in the bloodstream due to pressure changes when diving. "Nitrogen asphyxiation" search is more specific to the OP.

If you read the text of the link carefully, he did explain that he hyperventilated (breathed excessively) before breathing the helium. This overbreathing washed a lot of the CO2 out of the body, and, as he and I both explained, CO2 levels are what controls the level of breathing in normal humans. (By the way, I am also medically qualified and have also taught physics).

Just for completeness in some sense, I'll throw in carbon monoxide as a third mechanism of asphyxiation (or maybe for carbon monoxide it should be called poisoning).

The two things you mention, carbon dioxide and non-poisonous gases like nitrogen (and helium and argon), are not really poisons. You breathe them all the time with no ill effects as long as there is sufficient oxygen in the air.

Carbon monoxide works differently--when you breathe carbon monoxide, it combines with the iron in your blood so that the blood carries carbon monoxide (or a compound consisting of iron and carbon monoxide--I'm not really clear enough on what that is) instead of oxygen around your body.

Thus, even with plenty of oxygen in the air, the presence of carbon monoxide makes your blood incapable of carrying that oxygen around your body. (Which, obviously, will kill you under the wrong circumstances.)

All of the gases mentioned are odorless and colorless. Carbon monoxide at very low concentrations is enough to kill you.

And, it takes a fair amount of time for the carbon monoxide to work its way back out of your blood--the effects of carbon monoxide poisoning continue (and can get worse) even if you're out of the atmosphere containing carbon monoxide--it takes hours even approaching a day or more to get it out of your system.

Hmm, I guess this is OT, but I won't mark it as such, because I think it is important.

Would IG541 or IG55 be a better choice for halon replacement in manned area?

Halon rocks! Well..it used to.

There is a real mix of half stuff going on here.

Most people will operate fine at low altitudes and reduced O₂ levels which is what a nitrogen or CO₂ extinguisher causes by 'simple dilution'.

The standard pressure at sea level is 760mm Hg. Since oxygen comprises about 21 percent of the air, we would expect the dry air oxygen partial pressure in the lungs to be 159.6mm Hg (760 times 21 percent), but through physiologic processes, the partial pressure of oxygen in the arterial blood is normally about 100mm Hg.

Air inhaled into the lungs enters small air sacs (alveolus) where the exchange of oxygen and carbon dioxide occurs. When the partial pressure of the oxygen is higher than it is in the blood, oxygen molecules are picked up by the hemoglobin molecules. This hemoglobin saturation is approximately 97 percent at sea level.

Meaning you do not absorb all the O₂ in a breath. Nor do you breath out pure CO₂. If you did 'mouth to mouth respiration would kill the patient. Also meaning partial pressure - in the 'altitude sickness' sense is not a factor in the relative solubility of the gasses.

Neither is impairment of hemoglobin function a factor at sea level - [unless a source of CO is present, which is possible in a fire].

Respiration rate will increase if O₂ is scarce relative to demand - just as exercise induces. I.e you are still exhausting CO₂ but need to process more 'volume' to acquire the necessary O₂

So until O₂ levels fall to say 13 -15% - which would require a sizable extinguisher content, or a very small room, the O₂ stress is going to be less that skiing Aspen. Or flying in a pressurized aircraft. Or being revived buy 'mouth to mouth'.

What you will not have with nitrogen, is the same level of change of state cooling that CO₂ offers. Cooling has a great deal to do with extinguishing fire.

As CO2 is captured from the atmosphere, quite energy cheaply, (compared to nitrogen), put in bottles and re-released, so I fail to see what is 'not green'.

Question 2 is; Why would you replace CO₂ with something less fire effective and more energy expensive?

Most of this is 100% correct, but not the statement "Respiration rate will increase if O2 is scarce relative to demand - just as exercise induces. I.e you are still exhausting CO2 but need to process more 'volume' to acquire the necessary O2". The reason why breathing is driven to higher levels during exercise is that exercising muscle generates much more CO2, and it is the more CO2 which drives the breathing, not any shortage of oxygen. Breathing 5% CO2/95% O2 causes deep breathing. Breathing 10% O2/90% N2 will not at first result in any change in respiratory pattern, although in a short while breathing will simply stop. This inability to detect and respond to low O2 levels is what makes the use of the inert gases in confined spaces so dangerous.

Ummm - we are somewhat at cross purposes here.

True that working in confined spaces where inert gasses have displaced O₂ is dangerous.

An equivalent is a fire consuming all the oxygen, as happens when someone is asleep in a closed room with an oxygen consuming heater.

Or essentially, you are referring to prone inactive patients as above, and I'm referring to a fire extinguishing and evacuation scenario with a start point in standard atmosphere.

Key to 'not all stopping breathing' when the extinguishers go off, {which seems the worry in some quarters that started this} is time for O₂ deprivation to take effect - or what is "shortly"

Given we normally breath in around 0.03% CO₂ and exhalation is at around 7%, meaning some residual level remains in the lungs and the detection response works ± on that residual mean.

So increasing the 0.03% intake to 5%, will obviously 'stimulate' the response. As does the 7% in expired air resuscitation ['mouth to mouth']

"Flushing out" all residual CO₂, by hyperventilating, [like the idiot] obviously reduces the response, until residual mean levels are recovered.

So true; if CO₂ evolution is low due to absence of exertion, or supply from an external source, breathing may become shallow and even cease.

Again, the subject being at basil rate, is unlikely is a fire alarm scenario.

So "shortly" is the time it takes for CO₂ production to fall below the residual mean.

Prime cause for that is lack of oxygen intake? Agreed, yes/no?

If yes, then normal signs of anoxia will manifest in an awake active person.

Exertion ability will fall - just as 'running out of breath' and having to stop and recover the "oxygen debt". Along with blue tinge to skin, nails and so on.

As 'apprehension' is a normal response to fire alarms, increasing respiration rates are more the norm, but equally there is normally an increase in exertion raising CO₂ production.

So as said, dilution down to 10% is hardly a problem. Even 0 for a minute or so, is no real impediment to mobility.

If you are starting with "a fire extinguishing and evacuation scenario with a start point in standard atmosphere" then all is well. Everybody gets out into fresh air. What seriously worries me is the lingering idea that there is a safe time to carry on working in an oxygen-depleted atmosphere. There isn't. As I have explained, the normal human body does not respond with any kind of alarm signal to low oxygen. Apart from the blue colour of the lips (difficult to see in the dark and commonly missed even in good light) one of the earliest signs of hypoxia is impaired cerebral function, so you may have someone working in a low-oxygen environment deciding it is safe to go on working in a low oxygen environment. The next stage is that breathing stops, shortly followed by the heart stopping. At this point the worker is soon going to be an ex-worker: unlike the situation following a heart attack, where the heart has stopped but there is still oxygen in the bloodstream, the heart has stopped because of a complete lack of oxygen, and you have to fill the system again. Unless you have an oxygen analyser (or a canary) just don't even contemplate it.
For those still seeking some limits, and recognising that humans can live and work in the high Andes, I would point out that one can get accustomed to that sort of hypoxia, but acclimatisation takes weeks or months. For people who still want numbers, the transfer of oxygen from the atmosphere to the bloodstream is not a linear process, but I can provide some pointers for calculation.

Would it help if an intentional time delay between a fire alarm and cylinders discharge to allow personnel to evacuate the confined space before the automatic discharge takes place?

No - definitely not.

Every second you let the fire propagate adds a far greater range of perils than "diluting the O2 in the fires local environment"

You can look at fire propagation as logarithmic, so 'earlier on the curve' is a far better idea.

Given some products of combustion will 'kill you on the spot', or irrecoverably days later, I would think attacking combustion is 'more to the fore', than theorizing on what might happen to someone doesn't notice the fire in the room, the alarm sounding and jets of gas blasting. (Or the guy using the extinguisher) And/or is too dumb to stand up walk out and, ideally, close the door behind them.

As stated; it will take time for the 'dilution' to become 'perilous' and time again for that to hamper exiting the area.

Halving the O₂ has a massive effect on a fire, and little to no effect on people.

It also seems to be overlooked that the point of combustion is targeted by these systems.

Perhaps it's because in the movies 'all the sprinklers go off' - not just the ones that are trigged by the presence of fire.

The things that are fraught with this concept (as opposed to water) is leaks and other system failures.

As said in post #1, an alarm is necessary. This alarm should also link to O₂ level sensors throughout the installation (such as Westminster) And all these systems need a high rate of redundancy.

Also to be considered, is what happens with air conditioning systems and smoke handling - when the volume of the area is driven 'elsewhere' by the introduction of, and continuing supply of, gas, (until 'shutdown' by fire personnel)

I.e. I think this 'gas bank' idea is totally dumb. Nitrogen is "less than best". And above, are just a couple of other things on the list of "not immediately apparent" in a bank approach.

As a single extinguisher, N has some specialized merit in 'damage limitation'. Which is moot, if it fails to put out the fire, that CO₂ would have.

In 1983, I worked at a 3M tape plant, and part of my job was mixing batches of chemicals in a large tank, in a reinforced closed room, by manning a dead-man switch. There were 24 large CO² bottles set to operate upon the event of flame or explosion, and we were told that under 2000 lbs of pressure, the bank would fill the pretty much displace all the oxygen in seconds, and if we were unconscious, others would have a very short time to don the Scott Air Pak, and drag us out.

We had extensive training in ESD protection, and proper grounding techniques, fire training, etc, as well as the air pak training.

I never got to see it in action, but if the room has fluctuating levels of flammable vapour, I'd rather have the CO² to displace the oxygen... (their words... but does the 0² really go away? I dunno) but it felt good knowing it was there.

there is always more to learn....

Chris

as to hvac and fire, I think most buildings employ smoke dampers, which have links that melt with heat, and close automatically. (to limit oxygen supply to the fire, and provide a physical barrier)

the sensors of the system are wired for automated shutdown and damper close (to override the normally open outdoor and bypass dampers)

"but does the 0² really go away?"

Depending on the turbulence and means of application, oxygen will but pushed upwards out the vapor vent (provided for normal ventilation), quite quickly. "Seconds" is quite feasible.

The 'worse case' in this is of course, is being incapacitated by an explosion. But as least if the fire is rapidly quelled and the room temperature markedly reduced, rescue in that 'few minutes' is fairly achievable.

Were it a nitrogen dilution system - time to reduce the O2 to a non-supportive mix, may be similar, but turbulence may also cause intermittent flame fanning, so a longer time to 'safe to rescue'.

Arguments both ways - much depending on how you introduce the gas.

Directing CO2 into the vat at medium velocity would likely kill off a vat fire quickly. (likely well before the room was filled)

Doing the same thing with nitrogen may just initially suck/drag, surrounding air into the fire. Any flair up could give you the bang.

CO2 would only need to be maintained at a level about vat edge to safeguard against re-ignition. The balance of the room could be 'emptied' to facilitate medical intervention.

Nitrogen wouldn't 'sit' over a vat and continuing supply is unlikely to offer any guarantee against re-ignition, when rescuers open the door.

CO2 would flow out over the floor, leaving breathable air above, for rescuers.

Nitrogen would tend to disperse reducing O2 concentration over the surrounding zone.

You can smell/taste concentrated CO2, but not nitrogen

All in all CO2 is the hands down choice for this. And using a 'dead man' is the fastest and most reliable sensor they could ever employ.

Sounds well thought out - but glad you didn't find out

thank you... you continue to amaze with your depth of knowledge on every subject.

I misspoke myself.. it wasn't a switch I was operating but a deadman valve.. and I don't believe it had any sensors for monitoring other than me...

of course there were also pull stations... for what good they might be.

cheers

Chris

"Halving the O₂ has a massive effect on a fire, and little to no effect on people." I do not agree with the above statement. People can die even at 15% oxygen in atomosphere.

I just wanted to see what the effect of a 15% oxygen atmosphere would have on people--here's the first resource I found:

EFFECTS CHEMICALS HAVE ON THE BODY

"OXYGEN DEPLETION - Normal oxygen levels on the planet occur at 20.9 percent of total atmospheric gases. We can live and normally function with a minimum oxygen percential of 19.5. While life can be sustained at lower oxygen levels, function greatly deteriorates and can lead to death. The following chart shows effects of oxygen depletion (I tried to reformat the table to make it easier to read, but it is still easier to read on the original site):

• Percent of Oxygen in Air: Symptoms
  
• 20. 9: Normal
• less than 19.5: Respiration volume increases, muscular coordination diminishes, attention and clear-thinking requires more effort.
• 12 to 19.5: Shortness of breath, headache, dizziness, quickned pulse, efforts fatique quickly, muscular coordination for skilled movements lost.
• 10 to 12: Nausea and vomiting exertion impossible, paralysis of motion
• 6 to 10: Collapse and unconsciousness occurs
• 6 or below: Death in 6 to 8 minutes"

This table doesn't indicate that death can occur in a 15% oxygen atmosphere, but I suppose it can if you are in it long enough.

Interesting (to me) sidelight: I found some references (that I didn't attempt to read) that said that the oxygen in the atmosphere was as high as 38% as recently as the 19th century. I wonder if that is for real. If it is, that would seem to be a strong indicator of man's affect on the environment.

Ok, here's a reference to that statement (actually two references to the same base source, iiuc). Frankly, I don't believe it:

The detox book: how to detoxify your body to improve your health, stop

OXYGEN DEPLETION

The quote: "The earth's atmosphere contained 38 percent oxygen as recently as mid 19th century."

I don't believe that, either; with that much O₂, the world would have burned up in forest fires.

a lot makes sense to me.. what I'm reading in the first link. (on the health issues)(I don't know about 38% either.. but its possible. whether you measure in a forest, or in a desert, I imagine, makes a difference in O2 levels)

I'm very intrigued by the medical info in the first few pages of your first link.

whether you believe it or not.. thank you for the link. I will buy that book.

Chris

They may have got the date wrong

"Since the beginning of the Cambrian period 540 million years ago, O₂ levels have fluctuated between 15% and 30% by volume.^[50] Towards the end of the Carboniferous period (about 300 million years ago) atmospheric O₂ levels reached a maximum of 35% by volume,^[50] which may have contributed to the large size of insects and amphibians at this time.^[51] "

Wiki

^{bold is mine}

I am quoting following from the same source you have quoted. It is total mis-information and unbelievable.

"75 million years ago when dinosaurs roamed the earth the atmosphere contained 50 percent oxygen. Over time, the oxygen level dropped to 38 percent. Geologists attribute this decrease in volcanic activity, which reduced the escape of oxygen from igneous rock.
The earth's atmosphere contained 38 percent oxygen as recently as mid 19th century. With the advent of industrial revolution in the 1880s, which brought the burning of fossil fuels, industrial pollution, and eventually car exhaust. By the 1950s the percentage of oxygen in our atmosphere dropped to 21 percent. Although 21 percent is normally quoted as our current level, recent tests indicate that the oxygen level may now be at only 19 percent.
If you live in an industrial area your oxygen level could be as low as 11 percent, when the oxygen level drops to 7 percent you die."

I have not so far come across oxygen level below 20% in any industrial area, leave about 11%. Which recent test indicates that oxygen level now is only 19 percent. I have recently measured and found 20.8%. Assumption of 50% in past and 38% in 19th century is also absurd. We all know that since measure industrial activity started throughout the world in 20th century, change in oxygen percent in air is insignificant. More over even little increase in oxygen level reduces the self ignition temperature of combustible materials. At 38% it will be worse.

Well stay away from Everest base camp (about 10% O2) and the many parts of Nepal at 15%, like the 26 million locals do.

And if you ever go to the Americas - beware the mountains - because they maybe littered with the bodies of park rangers, hikers and skiers.

And what ever you do - don't hold your breath for a minute - especially when walking out of a burning building - lest you drop dead from using up more than 1/4 of the O2 you inhaled.

No - what you should do if these things go off and the building is low on oxygen and full of combustion toxins - is wait 48 hrs to acclimatise before proceeding - like the altitude sickness manual says.

Hardly worth mentioning, but air sacks would be "alveoli".

I know what a stickler for correctness you are.

I see a lot of good answers here.

As a fireextinguishing agent. It doesn't matter.

That fire extinquisher is for a first response to a fire. You only have time to use one extinguisher to control the fire. If you can't get it under control with that one extinquisher, then evacuate and let the fire department handle it.

It's not a problem for breathing with that initial response because that fire should still be small enough to contain.

The Number 1 hazard of that fire is NOT the nitrogen or carbon dioxide or powder or halon that the extinguisher contains. The #1 hazard is the smoke from the fire and if you don't know what is burning, there are things that burn that can kill you with only 5ppm.

That's why you have one extinguisher to control the fire. You don't use one then run and find another. If the fire is not undercontrol with the first one, it will be out of control for the second one and smoke will fill the air.

Nitrogen, CO2, Halon, Dry Chemical powder does not remove the heat from the fire, it only removes the O2. After a fire is out and Oxygen is reintroduced, you have the risk for a reflash. The only agent that will remove heat from a fire is Water.

So, bottom line...If you can't control the fire with the one extiguisher, don't try to be a hero, let the fire department handle it. They have breathing equipment for the job.

Janissaries,

A minor correction here. You say "Nitrogen, CO2, Halon, Dry Chemical powder does not remove the heat from the fire..." CO₂ is stored under pressure and is discharged as a very cold fog, with a measurable percent being deposited as a solid (dry ice) on surfaces. Although it does not remove as much heat from a fire as the vaporization of water will, it can and often does succeed in doing the necessary cooling of the combustible materials. Remember that it is classed as a refrigerant (R-744), and acts as one when it is discharged from a pressurized cylinder such as a fire extinguisher.

-JMM

No CO2 does not remove the heat from the fire. That cold is from the expansion of the CO2 from liquid form to a gas. It is not providing a cooling effect on the fire so don't be fooled by the frost forming on the cone.

Water lays on top of the surface and absorbs the heat. CO2 doesn't.

Another thing about a CO2 extinguisher is that if you don't ground the bottle as you are discharging it, meaning setting it on the ground, it will create static electricity and that frost is a conductor for electricity. The arc off off that cone when it isn't grounded is as much as 1/2" in diameter. So if you're not careful it could knock you down.

I do not know if Nitrogen discharge does the same thing.

Static was discussed extensively on this thread

No one ever said CO2 took more heat than water - but it does take heat and does deposit ice and/or water vapor.

This 'wetting' is one of the reasons for pure CO2's 'unpopularity' with fires in, or near, sensitive electronics.

To find out if nitrogen will do the same thing - compare the latent heats (assuming the same expansion parameters)

The use of nitrogen as a "clean agent" for extinguishing is in use today with certain restrictions. Nitrogen will "inert" the atmosphere of a room when introduced in sufficiency to extinguish a fire. In other words, the amount of nitrogen needed to DISPLACE enough oxygen to extinguish a fire will also displace enough such that life is no longer supported. If the area to be inerted is not occupiable, fire away. If the area IS occupiable, use 3M NOVEC 1230 as a clean agent. Is is colorless, odorless, and is environmentally your best choice. I am not humping NOVEC, just advising on an option.

Friends,

I have read all the posts. Candlez--yes, it can be clasified as a clean and environmentally friendly gas. Because N₂ and O₂ have only slightly different densities, it is difficult to blanket a fire with N₂ as a way of removing the presence of O₂. Therefore, the method of choice would be to add sufficient N₂ to dilute the percentage of O₂ until the chemical reaction of the fire stops. As many have noted, this also makes the space deadly for human occupants. In answer to the question in your post, I would not recommend its use in occupied buildings because of the very limited time you would have for evacuation and the complete absence of any way to detect the depleted O₂ in the atmosphere without special sensors. In other environments, it may be an appropriate fire extinguishing agent. Its use in those environments would have to be evaluated by a professional skilled in that type of work.

The transportation industry has a considerable amount of experience with N₂ as a fill gas for transportation of fresh fruit and produce, to slow the ripening process. Placards at the doors of the trailers warn that the workers must wait before entering until the fill gas has been effectively replaced by outside air. You can find documented cases where this didn't happen and people died.

People normally talk about the "fire triangle", of fuel, oxidizer, and heat. This triangle does not mention a fourth component, the chemical reaction that is propagated by the presence of free radical mono-atomic oxygen. Certain fire extinguishing agents, primarily the halogen ones, are excellent traps for this form of oxygen; their extinguishing effect comes from both smothering and trapping the reaction.

You may want to look to the NFPA (National Fire Protection Association) for further information and materials regarding your question.

--JMM

Would Inergen ie. IG-541 or Argonite ie. IG-55 be a better inert gas if we talk about total and automatic flooding system for closed and manned spaces such as substations and control rooms ?

The original question was "Can we consider Nitrogen gas a clean gas and friendly for the envirnment and health if it used as a fire extiguisher...", not "What is the friendliest gas?" Argonite is 50%/50% argon/nitrogen. Inergen is 52% nitrogen, 40% argon, 8% carbon dioxide. Both are proprietary (added expense), and offer no advantage over plain old N2. Indeed, if you happened to be stuck in an Inergen atmosphere, you would find it most unpleasant before unconsciousness supervened.

Nitrogen gas is definitely a clean gas but not friendly for the environment and health.

It is not clear whether N2 cylinder is planned are N2 piping. Cylinder may not be effective. If piping, then there is always danger of leakage or wrong operation. Auto release system in case of fire, N2 may harm more than fire. More ever N2 is best for stopping aggravation of fire, not extinguishing. If used by supply piping, a two valve system with a small vent in beween may be provided outside the building, to be operated manually in case of fire. Both the valves in the line are close and small vent open. In case of fire both the valves to be opened manually after evacuating people from the building. Keeping gas mask ready shall become mandatory.