Argon is a favorite gas used in many vacuum brazing shops, since it is an inert gas that will not react with any of the metals being heat-treated or brazed in those vacuum furnaces. Thus, dry argon (as measured by a dewpoint meter right at the furnace) is often used for partial-pressure brazing applications, or for rapid-cooling needs, or merely as a gaseous atmosphere to allow better conduction of heat between components inside the furnace. But argon can also be dangerous, and even lethal!
Argon is an odorless, colorless, tasteless gas, and because it is heavier than air it will flow to the lowest spot in your shop floor, often down into holes or pits built into your shop floor. Many companies build those pits in their shop floors so that equipment can be lowered down into them, thus eliminating the need to add height to the ceilings of the buildings. Then, when people enter these pits in the shop floor to work on the equipment, they may unknowingly be breathing argon that has flowed into and filled that pit, and then with no warning, they can collapse, having passed out from argon asphyxiation. If they are not quickly pulled out of the pit, they can die in a matter of minutes.
True story: Some years ago, a worker went down into a pit in a shop to work on the bottom of a tall piece of equipment, and apparently did not know that the argon being piped into his shop-area had been leaking and had filled that pit. As he was working on the base of the equipment, he collapsed from argon asphyxiation. His buddy must have been walking by the pit and noticed him laying on the floor of the pit, and must have quickly climbed down the ladder into the pit to see what was wrong with the first worker, and to then try to help him. This happened on a Friday evening. They were found in the pit on Monday morning, both dead, with the buddy slumped at the bottom of the ladder with the first guy on his shoulder.
Remember: Argon is heavier than air. Thus, it doesn’t really blend and or mix well with the air, but instead, tends to push it aside and replace it. As the pit fills with argon, the air is pushed out. Thus, no oxygen remains to support life!
Deaths from argon inhalation happen far too frequently in the metals industry, and the main reason for it is lack of awareness! Too many people believe argon to be a safe, inert gas, and do not take into consideration that it is heavier than air, and thus can be a danger to them when working in their shops. Thus, when folks use argon regularly in their brazing furnaces — or anywhere else in their shop – they must learn that escaping argon will always seek the low spots in their shop floor into which to “pool”, and that safety-steps must be taken to protect the shop-workers! The danger can be made worse if the argon supply valves are not turned off tightly, or if the argon-valve-packing is inadequate, and the argon is then allowed to slowly leak into any open cavity in the shop floor.
In every brazing seminar that I teach, I ask if people are aware of any deaths that have occurred from argon. In almost every class someone raises their hand and has a story to tell. When asked if they know of deaths that have occurred from other industrial gases used in brazing, such as nitrogen, helium, or hydrogen, no-one ever raises their hand.
Too many people are not aware of how dangerous argon can be, and that they can easily be overcome by the argon and collapse onto the floor of that hole or pit, since there is no smell to the argon (such as is placed in natural gas for our safety), and there are no warning sensations, no breathing spasms, etc., to warn you that you are in an argon atmosphere. When the brain uses up its oxygen reserves (since no fresh oxygen is being sent to it when you are breathing only pure argon), the brain merely shuts itself down, and the person instantly collapses. This can quickly result in that person’s death if he/she is not quickly pulled to safety.
How do we know that there are no advance warning signs to so-called “argon poisoning”? Because many people have been pulled out of such situations, having “blacked-out” and collapsed from their argon inhalation, and woke up in a hospital bed (or in the company’s sick-room bed), and are surprised to find themself there. When asked about any sensations they felt, or warning signs (such as dizziness, choking, lack of coherence, etc.) they invariably say that no warning signs occured at all. They were doing their work, and the next thing they knew they were waking-up in a bed! They were totally surprised by what had happened!
1. Oxygen-sensor. If you use argon in your shop, then always place an oxygen-sensor in any hole or pit in your shop floor into which people may enter. If the argon level gets too high, thus reducing the amount of air present, and thus the amount of oxygen available to breathe (there should always be about 20% oxygen in the air being breathed), the oxygen-alarm should sound-off loudly, and perhaps also be wired to a bright blinking-light, etc. (not just in the pit, but also in the shop area near the pit), so that anyone caught in that situation is immediately warned to get out of the pit!
2. Harness. Additionally, if the person needs to climb down a ladder to get to the floor of the pit, then it is also wise to be sure they are wearing a harness, with a rope attached to the top of the ladder (or to a railing around the top of the pit), so that the person can be pulled out of the pit without having to risk other people’s lives to have to go into the pit to try to bring that first person out.
3. Air-blower. It is wise to also have an “air-mover” (fan, blower, etc.) that circulates fresh air into the confines in which people are working. Make sure (by using a hose, flexible-piping, etc.) that fresh air is indeed being blown into the work zone from outside the pit or enclosed work-area, and have it blowing for several minutes before entering the space to work.
4. Respirator. If it is known that there is high-risk of argon filling the space in which someone must work, then it would be wise to have him/her wear a respirator-mask into which fresh air is constantly being supplied.
Note re bottom-loading vacuum furnaces: If the hot-zone is still very warm when anyone tries to stick their head into the bottom of the raised hot-zone, be aware that HOT argon will be much less dense than room-temp argon, and thus may not exit the hot zone as fast as one might think! Yes, there may be real danger even with a vertical hot-zone that opens on the bottom. Use wisdom, be careful!
Additional Warning re diffusion pumps: Argon can also be trapped in a diffusion pump. Someone reported a couple of years ago that a worker removed the top of a diffusion pump (poppet valve), then stuck his head down inside the diffusion pump while trying to reach down inside the diffusion pump to replace an O-ring, and was overcome by the argon trapped inside.
Welders — Beware! It is not uncommon for welders to work inside enclosed spaces, such as pressure vessels, etc., and their welding torches often use argon as the shielding gas. Unfortunately, many welders have been involved with argon-asphyxiation accidents, as described in this article, so welders, too, when entering enclosed spaces to weld, need to take proper precautions, such as: wearing a portable oxygen-sensor, wearing a harness, having an observer outside, wearing an air-respirator, etc.
Mike Mercer (Mercer Technoloies, Inc.) reports that it is possible to hurt your cooling fan motor if argon is used as a backfill gas, and suggests that a good way to protect the motor is to make sure that the cooling fan runs on 240 volts and not on 480 volts.