Dangers and Health risks of N2/LN2

[Xeon th MG Pony]

http://www.admin.ox.ac.uk/safety/s403.shtml

Asphyxia – Effect of O2 Concentration

O2
(vol %)
Effects and Symptoms

18-21
- No discernible symptoms can be detected by the
individual.

11-18
- Reduction of physical and intellectual performance
without the sufferer being aware.

8-11
- Possibility of fainting within a few minutes without
prior warning. Risk of death below 11 vol%.

6-8
- Fainting occurs after a short time. Resuscitation
possible if carried out immediately.

0-6
- Fainting almost immediate.
- Brain damage may occur, even if rescued.

4. Hazards
The hazards of liquid nitrogen are largely related to the large volume of gas produced on evaporation and to the liquid's low temperature. Its very low viscosity means that it rapidly and completely covers surfaces on which it is spilt and it easily penetrates cracks and voids. This means that any spillage on clothing will penetrate much more readily than, say, water. Large spillages on other surfaces may affect areas beneath the surface, by damaging materials or even by causing oxygen depletion in areas remote from the spill.

(a) Asphyxiation
On boiling, liquid nitrogen produces approximately 700 times its volume of gas. The resulting displacement of oxygen from the atmosphere may be sufficient to cause asphyxiation. There is no preliminary warning of oxygen deficiency caused by the addition of nitrogen. This is a significant hazard, which has been responsible for a number of deaths in research institutions over the past few years. In these incidents, asphyxiation is usually sudden. The victims inhale air with little or no oxygen content, causing immediate collapse into a layer of dense, cold, nitrogen-enriched air. Unconsciousness followed rapidly by death is inevitable without immediate rescue and resuscitation. Rescue attempts often result in the rescuers being overcome as well.

Smaller leaks or spills, or normal boil-off from liquid nitrogen containers in confined spaces (e.g. poorly ventilated small rooms, or cold rooms) may give rise to lesser reductions in oxygen content, but they may still carry a risk of asphyxiation. The risk of asphyxiation must be assessed wherever liquid nitrogen is used or stored, taking into account the volume present in relation to the room volume, the likelihood of leakage or spillage, the normal evaporative losses that occur with liquid nitrogen use and any ventilation arrangements.

(d) Condensation of liquid oxygen

The boiling point of oxygen is -183?C; therefore liquid oxygen may condense in open containers of liquid nitrogen or in open vessels cooled by liquid nitrogen (e.g. cold traps). Liquid oxygen will accumulate if the liquid nitrogen is constantly replenished, so this type of open cooling system should be avoided where possible. The unsuspected presence of liquid oxygen may give rise to explosions caused by increased pressure if the vessels are subsequently sealed and allowed to warm up. If oxidisable material is present, then liquid oxygen may react explosively with it.

http://www.osha.gov/dts/shib/shib042704.html < Link about Nitrogen related deaths in industry and how they happend & could have been avoided

http://en.wikipedia.org/wiki/Nitrogen_asphyxiation < Some more info for the Wiki lovers.

After seeing some comments from some users I figured be a very good idea to post this to make all aware that there is far more risks to LN2 other then just cold burns. Perhaps this thread would make a good sticky to warn others who may not suspect there can be more to using such a rather seemingly harmless gas. I have this all so in the LN2 & Dry Ice section.

[Brettbeck]

This thread should be deleted because you posted it in the DI/LN2 section aswell .

[Xeon th MG Pony]

Well it is applicable to both sections in a slightly different way so No I do not think it should.

Here it is applicable due to purging and the use of high pressure nitrogen cylinders, in the D/I-LN2 section it is applicable due to volumetric expansion of evaporating LN2 and the possibilities of spills, since most newbs will not go into both sections there is a high chance they will not see one or the other.

Thus my decision to place it in both forums to ensure it will be read by thoughs it will directly effect.

[Brettbeck]

OK if you say so.

[[XC] gomeler]

Agreed with Xeon, purging/brazing in a terribly ventilated place can result in the displacement of a large portion of the oxygen, leading to asphyxiation. First step though should be to perform such work in a well ventilated place, nothing better than a driveway.

[Xeon th MG Pony]

Well I do most my work inside, how ever I have the doors wide open along with the window In shop I use a vent fan running mid range as to keep the noise down. The thing here is ALL of this applies to refrigerants too! How ever refrigerants have auxiliary effects that can be seriously dangerous, such as acting as an anaesthetic and such, so even if no O2 depletion it will still effect your ability to perform in an emergency.

Walt goes on about pressure safety and such which is good, yet seems he and most have missed the mark on the gasses them selfs. I think it is time to shift some focus on the very heart of the system, the gas which makes it all possible and their risks.

[Exahertz]

In the house im restoring, im building a lab with some large counter tops and a fume hood over a deep sink.

the blower that will power the fume hood is an Elmo Rietschle 2Bh type

so ventilation shouldnt be an issue!

[Xeon th MG Pony]

lol next you'll be doing vacuum metal plating

[[XC] gomeler]

Wow, wish I could build a fullscale lab in my house Would be so much fun to have a dedicated workspace, garages have to be shared with cars and you can never have too large of a garage. Nice stuff Exahertz, I'm jealous.

[Exahertz]

lol next you'll be doing vacuum metal plating

I used to work on the University Of Maryland's campus making multilayer x-ray optics for researching a new type of Computerized tomography (CT) scanner, so at one point I was making DC magnetron vacuum sputtered mirror coatings of a 2 angstroms degree of precision smoothness using platinum and carbon multilayer.

I just thought it was funny that you said that, as i already have done that

[Xeon th MG Pony]

I was thinking of trying to make a Vacuum plating machine of a very small scale for making CO2 Laser mirrors, but then started to switch carreers into phase change so stopped investing money in such projects. Would been a blast though lol.

[wdrzal]

Well I do most my work inside, how ever I have the doors wide open along with the window In shop I use a vent fan running mid range as to keep the noise down. The thing here is ALL of this applies to refrigerants too! How ever refrigerants have auxiliary effects that can be seriously dangerous, such as acting as an anaesthetic and such, so even if no O2 depletion it will still effect your ability to perform in an emergency.

Walt goes on about pressure safety and such which is good, yet seems he and most have missed the mark on the gasses them selfs. I think it is time to shift some focus on the very heart of the system, the gas which makes it all possible and their risks.

more bs, as purging uses no oxygen and neither does brazing if using a 2 gas torch.)o2/acetylene) if using a single gas + air torch ,you can braze all day and not use .5% oxygen, unless your brazing inside a fridge with the door closed,your body uses much more.

[Xeon th MG Pony]

This has nothing to do with O2 usage, it has to do with Nitrogen usage, and even then it isn't what I would call a risk, How ever potential fumes are a risk, and I do not know about you, but I do not enjoy inhaling toxic fumes from oil or any trace amounts of refrigerant so No bs here. Same reason why I don't smoke and dislike people smoking around me, I do not like inhaling toxic fumes, thus good ventilation is all ways a good practise no mater how little O2 the torch(s) consume. Purging you are quite correct it doesn't consume O2 (Kinda obvious ya know ) and the flow rate used would probably take years to displace the oxygen. I think you direly missed the point here Walt.

You of all people should know that when using any gas supplied device you should ensure good ventilation, and even more so when working on refer units that have oil residue in them (Unless it is OEM). This is beyond proven by WBC, OSHA, and other such worker safety boards.

[SexyMF]

Xeon it all seems ironic given your signature.

[wdrzal]

well you started out with a post about oxygen deletion levels and the effects,well I have not only read about the subject but experienced o2 deprivation first hand in a altitude chamber.

toxic fumes can also over come someone when brazing.

but sexymf is correct,kinda ironic of you teaching safety with your Darwin award of natural selection.

you need to practice what you preach,all ways, just not when convenient.

I use a portable supplied air system when any question of possible dangerous fumes exists.

[Xeon th MG Pony]

My sig has far far too a long of a story behind it to explain the logic behind it.
Any way, a lack of parenting and a failure of modern society to teach kids to think critically is not a failure of the kids genetics, and thus teaching safety is not ironic to the sig, how ever after they are aware of the risks and still do some thing in a patently dangerous way, then I'm sure they'd win a Darwin award.

I have a nice dual cartridge chemical mask that I wear when de-brazing old systems when I can not get a good flow of air to ventilate my place out.

[serialk11r]

Xeon, N2 is not toxic, its the potential of LN2 to reduce the concentration of oxygen that is potentially dangerous. Now it seems you're trying to say you don't like toxic things...which...

[Xeon th MG Pony]

No I do not like inhaling them, N2/LN2 is not toxic.

Walt made a comment on my comment about ventilation because he missed the fact there are more factors then just O2 levels, which I expanded on my statement by reminding that there is other reasons one should ensure good ventilation even if O2 depletion is not an issue.

[SoddemFX]

I think having accurate &#37; is all well and good but fairly irrelevant as wouldn't you just make sure you have good ventilation before you started?

Aside from that i don't think there are many (if any) people here who have equiptment capable of measuring these quantities...

Ah well, i'm going to make a cup of tea - i'd best remember not to inhale it

//Edit - the oxygen fact is quite interesting tho...

Tom

[boshuter]

You forgot to say "don't drink it" too...

[Xeon th MG Pony]

Actually tea is healthy lol, just make sure to follow the safety requirement of drinking plenty of water as it is a diuretic! lol

[Xeon th MG Pony]

I think having accurate % is all well and good but fairly irrelevant as wouldn't you just make sure you have good ventilation before you started?

Aside from that i don't think there are many (if any) people here who have equiptment capable of measuring these quantities...

Ah well, i'm going to make a cup of tea - i'd best remember not to inhale it

//Edit - the oxygen fact is quite interesting tho...

Tom

You'd think but lately tons of people have died from running generators and the like in enclosed spaces, so now my motto is "never under estimate human stupidity/ignorance" I realy have no clue what the hell our schools are doing now days for the life of me, but they sure don't seem to be teaching people to stop and think of the golden rule: Every action has an equal & oppisit reaction!.

[Exahertz]

Every action has an equal & oppisit reaction!.

Thats Newtons 3rd law pretaining to the kenetic mometive force of one object acting upon another. But i guess it does make sense as an aphorism too.

[Xeon th MG Pony]

Thats Newtons 3rd law pretaining to the kenetic mometive force of one object acting upon another. But i guess it does make sense as an aphorism too.

Hehe yup, glad to see it isn't lost out there is cyber space, I was worried some wouldn't understand what I meant by it.