Inert Gas Colouration

I am confused by your 'considering the number of people killed'

The only gas I that causes a number of deaths each year (to my admittedly limited knowledge) is Carbon Monoxide (CO). Unfortunately, it is 'manufactured' on-site by malfunctioning burners in space heaters or fireplaces. There ARE low cost CO detectors that will emit very loud shrill sound impossible to ignore when CO levels reach high, but still safe concentration.

It IS possible to add tell-tale odor to any gas, methly mercaptan being the one used in natural gas distributed to homes and businesses.

Inert gas such as Argon kills a number of welders each year.Oxygen sensors are available but not fool proof as they can fail. I raised this for discussion to see if there was some kind of foolproof way of sensing this hazard.

My own father tried to save a welder about twenty years ago who had been asphyxiated by Argon (unknown by my Father). Unfortunately the welder a young man of 24 years died on my Father's back and my Father went into a coma and was fortunately ok.

Had there been some foolproof way of detecting this for them both this unfortunate incident could have been avoided.

Hi Joseph,

During my time with a pest control company in Durban, S.A. we used a highly toxic product to fumigate houses contaminated with Crypto Termes Brevis (West Indian dry wood termite) Methyl Bromide often had a tear gas warning agent included in the canister. (Bromethane?). What I'm not sure about is whether the inert gas would react with something like tear gas.

Anyone else out there with some idea?

I think you must be able to mix any gas with an inert gas. If the gas is inert it will not react with an other gas, but you always can mix.

Inert gas (nitrogen, argon, helium etc) is not itself harmful, rather, it is dangerous mainly for the fact that its presence in large amounts displaces too much air (and its 20% oxygen) resulting in a suffocation hazard. However most processes that require inert gases do not want adulterants present, and many can't tolerate them at all.

Perhaps the ultimate answer you seek would be to have an oxygen sensor that would alert when sensing the presence of an unsafe (low) level.

If you are including gases that are actually harmful themselves, such as CO (carbon monoxide), that results in many deaths, and is best guarded against by the use of the appropriate detectors. CO detectors are easily obtainable and inexpensive. Methane is another dangerous gas, largely for its ability to displace breathable air, and methane detectors are also available, but they are more expensive.

Regards, Greg

Inert gas a killer? Huh? The thing to worry about, after detecting harmless gas, would be to get rid of the colorant left behind...before it kills the looks of something.

I am not sure if you are just being facetious or sarcastic or both?!!? Any gas, in sufficient quantities, regardless to its composition or whether it is inert(such as the noble gasses, group 8 on the periodic table) or not, will cause suffocation ergo they are killers in the right environment and under the right circumstances.

Contrary to Greg's comment though, it should be noted that CH4 (methane) is more well known by its other delightful characteristics, that is to say up to 5% concentration it burns(making it a useful industrial gas) from 5-15% it explodes(as happens quite frequently on South African gold and coal mines) above 15% it displaces oxygen ergo suffocation.

Technically the inert gases do not harm you or have any substantive effect, You can breath helium/argon if sufficient oxygen is present. It is the insufficiency of oxygen that kills. In the particular narrow application discussed here the inert gases are used to displace oxygen and lower the concentration of oxygen in the immediate atmosphere. During welding other gases can build up also, and since the concern here is the adequate presence of oxygen, this is what needs to be addressed.

Maybe I was just pointing up, in a somewhat sardonic fashion I must admit, what the original query seems to suggest: a highly toxic gas which could kill large numbers in short order--in places, presumably enclosed spaces, where both large numbers would congregate, and where escape would be difficult in short order. Since it is hard (for me at least) to envison such a scenario--or very many such scenarios where lives formerly lost might now be saved--I was led to interpret that it might be "non-reactive toxic" gasses that was being referred to. Suffice it to say, I posted with full intention of being corrected or enlightened. Therefore, thank you.

A slight correction. Mixtures of flammable gases in air have what is known as an upper and lower explosive limit. Below the Lower Explosive Limit (LEL), and above the upper explosive limit (UEL), the gas/air mixture cannot be ignited. In between the limits, the mixture explodes. The limits for methane are 5%-15%.

Below 5% methane does not burn.

Tad

Hi Tad,

I am aware of the UEL and LEL of methane, I believe the most volatile level being in the region of 9.2%. However what I do disagree with is the below 5% burn. Hydro Carbon gasses do burn a certain percentages, don't forget the normal cigarette lighters (no guys, not a Zippo). Mine college training indicated the percentages and my current studies in chemical engineering also point to this.

If you have a link of some such that indicates otherwise I really would like to take a look at it. Perhaps its just me that fell off the wagon.

Thanks.

Hi Mongoose,

Maybe we are talking about 2 different things. The LEL and UEL are the lower and upper percentages that a fuel/air mixture will ignite or explode, by definition. Any site or reference I send you to will give this definition. This refers to mixtures of fuel and air that can normally be ignited, the normal safety situation that one must guard against.

I can see other situations where low concentrations may "burn", such as sending 4% methane through a heated catalyst.

In your lighter example, this is 100% fuel burning in an air environment which would seem to violate the UEL. However, the fuel is only burning on the outside of the flame, where it would be mixed with air.

Can you explain your definition of burning outside the LEL and UEL?

Tad

Hi Tad,

I think I may have confused the issue, need to go look for my Mining notes. I do, however remember an incident in one of the deep level gold mines where I worked. On a entry examination by myself and the miner I was to relieve(he was going on leave), we discovered one of the shot holes blowing gas. A methanometer reading indicated a 3.5% concentration. This old guy promptly took out his cigarette lighter and fired the hole, I will not discuss the merits of such an action, but suffice to say after a flame thrower effect lasting about 5 minutes, the pocket of gas burnt out.

What exactly happened in this case, I can only dare to guess!!

Mine training as far as gasses go is basic introductions, characteristics and dangers associated with them. I will at this time stand under correction, and say thanks for your comments, they will certainly help in my current line of study.

Fuel gases are, by definition, not inert as they react with oxygen; "natural gas" in the UK, mainly methane, does not smell by itself, and an odour is added before it is distributed so that for domestic users there is a method of detection (the nose). The odourant is burnt along with the gas.

For a gas to be useful because of its inertness, like argon, there cannot be an odourant added as the presence of the odourant will reduce the inertness of the mixture, making it useless as an inert atmosphere.

The original post wanted an odourant added to an inert gas to reduce the risk of death by asphyxiation. The absence of oxygen, and its monitoring by personal monitoring devices coupled with appropriate procedures and training, is about the only way to effect what the original post requires.

A sideways glance: the LD50 for Pu in humans is about 7*10^-15kg/person. The LD50 for H₂O in humans is about 8.2kg/person; one can drown in 2kg...

Hi Joseph, welcome to CR4

when you consider the amount of people killed

The only way an inert gas can harm you is asphyxiation. Inert gasses by their nature will not react with anything whatsoever chemically and this means they are completely non toxic. They can however displace all the oxygen in the air and as a result you suffocate. Helium is lighter than air so it's pretty hard for it to build up anywhere but the denser ones can accumulate in tanks and depressions that don't have adequate ventilation

Adding something to an inert gas has a couple of problems that spring to mind. Firstly inert gasses are often use specifically because they are inert so adding something that smells will render the inert gas useless. Keep in mind that for something to have a smell it must be chemically active. Secondly anything that you add to an inert gas will tend to settle out with whichever gas is denser at the bottom. Now since the only place that I can see inert gasses being dangerous is where they can settle any additive would separate out and this sort of defeats the purpose of adding it in the first place.

Inert gasses are not that common and I havn't heard of anybody ever being suffocated by them but that doesn't mean it hasn't happened. At any rate anybody that is likely to be exposed the dangers associated with inert gasses should be well aware of them and understand the precautions that need to be taken. Also adding anything to them may be a waste of time and may render the gas useless and I suspect this is why it isn't already done.

Perhaps a better way to provide the protection required would be to detect for reduced levels, or the absence, of oxygen, and to provide appropriate training.

Many suitable personal appliances are in use widely in confined-spaces-entry operations across the globe.

It seems that since the problem with inert gases must be asphyxiation and that is not likely in non-enclosed spaces or where oxygen (or air) is available. Perhaps a detector is not what is needed. As you say, training should be required and development of procedures to guarantee that the individuals are safe. Use of air-packs, etc. are often required in most industries before entering an enclosed vessel or space.

Training for hazardous "gas situations" is always critical, even beyond inert gases and CO gas is among the worst. In the 1970's 13 Blast Furnace workers were killed at a Chicago area steel complex when a blast furnace stove connection (pipe) handling large volumes of CO collapsed resulting in the gas being spewed into the open air. Even in unconfined areas some gases such as CO, NH3, HCN, etc. are dangerous.

Indeed. Training and personal gas monitors are required in the water supply and disposal industries in the UK, where things other than inert, such as H₂S or "bad egg gas", are occasionally present. Above 50ppm, H₂S knocks out the nose's sensors, rendering it undetectable otherwise than by using equipment!

Isolation and lock-outPermit-To-Work, Confined-Spaces-Entry-Permit, wearing a working personal gas monitor, a Standby Top Man, a body harness and a winch to haul out the worker unfortunate enough to be selected for confined space vessel entry, are the norm.

Recently, three UK workers were asphyxiated and a fourth had a narrow escape when being unable to escape from a large sludge tank located at a farm. There was insufficient oxygen within the tank to sustain life. Prosecutions are underway, according to news reports.

There remains in the history of South African mining disasters, one particularly horrendous episode where 177 mine workers died. The Kinross mining disaster inquiry found that artisans had been working on the steel pipes, which were at the time covered in an insulated cladding plus plastic cladding on cables and the poly urethane tunnel cladding caught fire from an acetylene torch spark. The resulting gasses released included CO and COCl₂. The flames and resultant gasses struck with such speed that the lads fell where they stood, not even having sufficient time to activate their rescue packs (a self contained re-breathing device). All the training in world will not guarantee anything is fool proof, because fools are so damn ingenious!!!!

I had at the time just started my mining career....?

Hmm, CO and COCl are not inert gases. Inert gases must be employed, not generated by accidentally burning plastic. In this case proper safety procedures, confined space entry permits, and lock-out tag-out would be sufficient, if properly employed.

Hi Guest,

Your comment is valid. My comment was just a piece of information you can store in your file of useless information. What however I would like to bring to the forefront of this thread is that Man in general has not been able to nullify the poisonous, acid and explosive gasses, how the hell is he going to start dealing with inert gasses.

Anyone that has worked on a chemical plant, refinery, deep level or coal mine will know of the protocols introduced in these environments to prevent injury and loss of life...............................yet people continue to be killed on these sites.

Maybe I'm being overly pragmatic (or some other such word with a suffix ..tic, related to the moon).

Fail safe precautions usually fail because of failure in equipment, people and environments??????.

P.S. Why don't you join CR 4?

Can I assume that your question about a UV trigger indicates a potential release of gas to the surrounding environment? I should think that in that case a good chance for substantial dilution of the gas exists. If this is a manufacturing environment the Health and Safety staff should review and address any concern where inert gas could collect, displacing air and potentially lowering the O2 content. This would call for air monitoring, engineering controls to prevent the condition and personal protective equipment for staff with exposure potential. Of course this comes with a training requirement as well as evacuation route planning.

Site specific health and safety plans are commonly used by contractors to anticpate and address potential issues which could lead to hazardous exposures.

Inert gases are a significant danger in many places. For example, in chemical plants large quantities of N2 are used for instrumentation and purging of enclosures to meet explosion proof requirements. The instrumentation is often housed on a small building. If ventilation in the building is interrupted and/or there is a large N2 leak, it is possible for N2 to displace the air, and people have been killed.

The most dangerous thing is that there is absolutely no warning when a person suffers from oxygen deprivation. There is no mechanism in the body to warn of lack of O2. The person feels fine, has maybe about 5 seconds of tunnel vision and collapses.

Hi Joseph

The only way to minimise this danger is to apply the strict safety procedures required before entering a vessel or room which has had such a gas in the specific enviroment.

Most first world and many third world industrial laws have very detailed and specific procedures for working in areas which may have residual gas pockets. These include using specialised monitoring equipment and wearing the appropiate PPE. UNDER NO CIRCUMSTANCES can a worker be allowed to work in such an enviroment and must have an attendant worker capable of rescuing him when necessary. There will never be a fool proof system whilst people are involved.

How about an Argon Leak Detector!!

http://www.avem.org/MemDirF/VIC.html

An infallible device such as ones nose or eyes would eliminate such fallible items!

As above, an inert gas would cause no indication at the nose, as by definition, inert gases have no chemistry with which to cause the indication.

As above, H₂S levels exceeding about 50ppm knock out the nose's sensors.

All inert gases are colourless. Colour is introduced by condensing vapours or finely-divided particulates, giving scope for separation of the colourant from the gas. One is no better off.

"Absence of oxygen" is standard monitoring practice across a wide range of industries, for which a wide range of equipment exists, coupled with extensive training. An employer stands exposed to be prosecuted for failing to do this.

The problem is the "infallible devices you are counting on, is that they are anything but infallible. Among others mentioned in reply #25. Your senses are not sensitive enough to pick up most chemicals in time to save your life. In other words, by the time you have smelled a chemical, it is too late. The lack of oxygen in your body dulls your senses; a gradual decrease in oxygen would go undetected until it was too late for you to do anything about it.

To prevent a Hazardous incident, proper training, proper Personal Protective Equipment (PPE), and proper air supply is mandatory and required by law in North America as well as most places in the world.

If a supervisor does not ensure the workers are provided the proper training and PPE, they are liable.

For every known chemical used in the industrial, there are tools to measure concentrations. There are proper handling procedures, and spill response procedures developed.

There are two main reasons that companies do not train thier workers properly

1. Money
2. Ignorance

For information on any chemical check these sites

http://www.cdc.gov/niosh/homepage.html

http://www.tc.gc.ca/canutec/en/menu.htm

Here is another

http://lacotech.com/product_pages/GasCheck_Handheld_Sniffer_Leak_Detectors_2385714426.html