Deco Cylinder Mishap

[DTm]

In an extremely oxygen enriched environment the ensuing fire is often so rapid, hot, and violent that it mimicks in all regards an explosion! Oxygen is an extreme accelerant! There are several videos on youtube that demonstrate this phenomenon! Simply do a search for "oxygen tank explosion".

In the hospital we try to never store oxygen (or any flammables, for that matter!) in enclosed or poorly ventilated areas. What you want to avoid is the build-up of high levels of oxygen or flammable vapors in a confined area. In the OR we have a waste gas system that actively removes the spent anesthetic gasses and oxygen to the outside of the building. And if we are doing a procedure under local anesthesia or with sedation and the patient is wearing a simple O2 mask or nasal cannula, we make every effort to ventilate the area around their face and suppress any possible ignition sources. An OR fire can be disasterous! And keep in mind nitrous oxide ("laughing gas") is just as vigorous an accelerant as oxygen!

I can easily see where an unnoticed leakage of 100% O2 in an enclosed vehicle could cause exactly what you saw with David's truck! Personally I think it is a much better idea to carry such tanks in the open bed of your truck where any leakage can simply escape into the atmosphere and not reach a "critical" concentration! And if you must carry them in the passenger compartment make sure windows are cracked and there is a constant turn-over of the air within the car. (Read that as "well ventilated"!)

While the O2 may not explode, keep in mind that on a vechile that are other fuel sources that do and if in fact a concentrated O2 level did happen it would have made that explosion more viloent, might have even lowered thier flash point.

 

[Dive-aholic]

I have been criticized for being lazy because I do this... but I agree. My regs stay on my deco bottle all the time, unless it's being filled.

I guess I'm lazy, too, then.

How long do the bottles go between use or fills?

What does that matter? I sometimes use my O2 bottles every day. Sometimes I won't use them for a week. I use my 50% bottles maybe once a month. Regs stay on the cylinders.

I think the best idea to prevent an accident like David’s is to make sure that your O2 is stored and transported in a well-ventilated area and away from fuels. If it is in the bed of your truck great - if it is in the cab or passenger compartment crack a window. Make sure all your tanks are secured to prevent falling.

Some of us don't have that option. Those of us who own vans or SUVs have to keep the cylinders inside. A cracked window will not be enough. You'd have to keep all the windows completely open. The only windows in my van that completely roll down are on the front doors, 10 feet away from where my O2 bottles are stored. While the rear windows will open a little, it's not enough to ventilate the area sufficiently.

 

[Hatul]

Someone correct me if I am wrong... even though these plastic DIN plugs might vent the leaking 100% O2 in the deco bottle wouldn't that create situation of putting or having hydrocarbons in a pressurized O2 rich environment just in the space between the value and plug - thus lowering the flash point of the hydrocarbon and thus creating the ignition source.

I do not know seem like from what I know putting a plastic cap on would be a worse idea than a metal one. The metal ones sound like a they are a bad idea too, at least they would wait till you wrench them off. The idea of having the reg on them seems like it might be a good idea - with the concept of just containing the O2 from a cracked (slightly opened) value, or a bad value. While we cannot plan/prevent for every miniscule event, what happens if the regulators also free flows?

I think the best idea to prevent an accident like David’s is to make sure that your O2 is stored and transported in a well-ventilated area and away from fuels. If it is in the bed of your truck great - if it is in the cab or passenger compartment crack a window. Make sure all your tanks are secured to prevent falling.

There is so much we do not kno.w about David’s actual accident. I am not sure any of that would have prevented.

I wish David well and hope to see back out at the lake soon.

What happens with the plastic plugs when you open the valve is the thing makes such a loud sound that you can't miss it. With the vented valve it does not heat up so there's no source of ignition of the plastic.

The steel plug may be safer still as it seals totally the gas flow out, and you'd know the valve opened when you try to remove the plug. If you find the plug under pressure you'd naturally close the valve before continuing to unscrew the plug. This may be the best solution for O2 in a scuba tank.

With the reg on the valve there is a risk of free-flow but you'd hear it as with the plastic plug.

 

[DTm]

What happens with the plastic plugs when you open the valve is the thing makes such a loud sound that you can't miss it. With the vented valve it does not heat up so there's no source of ignition of the plastic.

The steel plug may be safer still as it seals totally the gas flow out, and you'd know the valve opened when you try to remove the plug. If you find the plug under pressure you'd naturally close the valve before continuing to unscrew the plug. This may be the best solution for O2 in a scuba tank.

With the reg on the valve there is a risk of free-flow but you'd hear it as with the plastic plug.

If a tree falls in the forest but no-one is around, did it make a sound?

If we look back at the reports from David’s accident {David heard a hissing noising and went to check on his tanks}. Given that - how does having a plug that vents or a second stage that possibly free flows (might even be from just ambient pressure on the surface) making a sound help prevent this from happening again?

A value with no plug or regulator on it… still makes a loud annoying sound. David heard it, and was trying to address the issue...

I do not understand a lot about the hydrocarbon and O2 issue - just that it is a bad mixture for the most parts. What I thought I understood was it is not really about a heat source being applied, such as the reaction of a gas being compressed heating up - but a reaction issue of the hydrocarbons with higher O2 concentrations. The hydrocarbons and the O2 cause the reaction and thus the heat source and ignition source.

Maybe the right answer is the run away answer - or maybe it should be clear the area and wait for several hours before approaching.

 

[The Chairman]

Maybe the right answer is the run away answer - or maybe it should be clear the area and wait for several hours before approaching.

The simple act of opening the car door and having the lights come on could have very well been the spark that set the mixture off. We often grow used to the smells in a vehicle, but they come from the gases in your car. Adding a good amount of oxygen to the system makes it volatile.

I understand that there are two videos on Youtube about the explosion. I found one and was underwhelmed. Nothing to learn from it. I can't wait until David can come give his version of the events.

 

[mselenaous]

Video links from local news:
Witnesses Recall Explosion At Parking Garage
Fire & Explosion In Parking Garage

Video link from You Tube, "man on the street" outside the building:
explosion in downtown austin - YouTube

 

[Hatul]

If a tree falls in the forest but no-one is around, did it make a sound?

If we look back at the reports from David’s accident {David heard a hissing noising and went to check on his tanks}. Given that - how does having a plug that vents or a second stage that possibly free flows (might even be from just ambient pressure on the surface) making a sound help prevent this from happening again?

A value with no plug or regulator on it… still makes a loud annoying sound. David heard it, and was trying to address the issue...

I do not understand a lot about the hydrocarbon and O2 issue - just that it is a bad mixture for the most parts. What I thought I understood was it is not really about a heat source being applied, such as the reaction of a gas being compressed heating up - but a reaction issue of the hydrocarbons with higher O2 concentrations. The hydrocarbons and the O2 cause the reaction and thus the heat source and ignition source.

Maybe the right answer is the run away answer - or maybe it should be clear the area and wait for several hours before approaching.

I just don't see how you can get plastic to explode just exposed to O2 without a heat source. After all, we run oxygen thought all kinds of plastics at the hospital.

 

[fdog]

Having been on my hands and knees, slipping and sliding on molten carpet as oxygen bottles in an apartment intensified the fire around us:

I am quite certain that a high O2 concentration will take normally stable things and make them burn so rapidly as to be percieved as an explosion.

It will still take some heat, in the form of an ignition source. However, because that ignition source may be so small (such as a spark from static electricity from sliding pants over a driver's seat) we won't perceive it as a conventional heat source.

***************

More to your question:

It's a matter of surface area. For example, an ice-cube sized block of aluminum will just sit on your desk like a lump and behave like...well...a lump. Grind that block of aluminum into a fine enough powder, and it will spontaneously ignite on contact with ordinary air, as the tiny particles are surrounded by oxygen, forcing a reaction.

That ratio - small enough amounts of aluminum to a large amount of oxygen - can make (usually) benign aluminum shavings, like what's leftover from machining processes, behave exactly like the powder, when it's placed in a 100% O2 environment.

Now, consider the inside of the passenger space of a vehicle. Reflect on the large volume of burnable materials - carpet, seat fabric, huge blocks of urethane foam, headliner fabric, and more. These burnable materials are fuel. And consider on how almost all these things have a very small structure (like fabric) with a huge surface area.

Imagine that huge fuel load, with a high surface area, saturated with 100% oxygen. It's primed to burn if only insulted by the tiniest spark, and the rate the fire spreads will be perceived as an explosion.


All the best, James

 

[ianr33]

More to your question:

It's a matter of surface area. For example, an ice-cube sized block of aluminum will just sit on your desk like a lump and behave like...well...a lump. Grind that block of aluminum into a fine enough powder, and it will spontaneously ignite on contact with ordinary air, as the tiny particles are surrounded by oxygen, forcing a reaction.

That ratio - small enough amounts of aluminum to a large amount of oxygen - can make (usually) benign aluminum shavings, like what's leftover from machining processes, behave exactly like the powder, when it's placed in a 100% O2 environment.

Coal dust is another good example. It's rather hard to light a single lump of coal,but when powdered, coal is explosive.

Coal dust - Wikipedia, the free encyclopedia

 

[DandyDon]

Coal dust is another good example. It's rather hard to light a single lump of coal,but when powdered, coal is explosive.

Same for many powders. My daughter told me about their big, dirty, patio grill catching fire and how they threw flour on it until it went out. You actually see that suggested at times online, but it can flash fire explode. Many grain elevators exploded before they learned to control that. I gave her a large can of baking soda to keep by the grill, another for the kitchen. I think I like a waterproof can of baking soda better than a fire extinguisher for a kitchen for a couple of reasons.