Film-Tech Forum ARCHIVE: My soda machine tried to kill me

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Posted by Mike Blakesley (Member # 26) on 04-20-2017, 08:34 PM:

Last Sunday I had something happen that I've never experienced in 38 years of running this place. When I got to the theatre and poured my customary soda, I noticed that the CO2 was out, so I went downstairs to change the tank. I was about halfway thru the process of taking the regulator off the tank when I noticed I was getting short of breath, and then I noticed I was feeling lightheaded and my vision was starting to get "sparkly" around the edges. I knew I was about to black out, so I raced to the stairway back up to the office and headed for a chair. It took about 2 minutes for me to fully catch my breath again, or at least it seemed that long, and then I was left with a headache for about half an hour.

It turned out that for some reason, just before we got there to open the theater, the CO2 tank had "outgassed" into the room. The basement room where the tanks are is only about the size of a small closet, so the air was pretty thick with the stuff.

This is an 87-year-old building, so the basement always has kind of a moist/musty smell to it, so I didn't notice anything amiss when I went down there.

I think if I'd stayed another 20 seconds I probably would have passed out and my friend Keith (a paramedic) said I could have died, or had brain damage, if nobody came to my rescue within a few minutes. So, I'm glad I had the smarts to get out of there when I did.

We put a fan at the basement entrance and blew fresh air down there, and it took maybe 15 or 20 minutes to clear the room of the CO2. Pepsi-Cola replaced both the outgassed tank and the gauges assembly to be safe, because we couldn't see any problems with the O-rings on either the tank or the gauges. I suspect the tank was the problem.

All ended well, but I just thought I'd pass along this story as a warning to anybody else who might feel light in the head while changing a CO2 tank. It's nothing to mess with.

Posted by Dennis Benjamin (Member # 1137) on 04-20-2017, 09:17 PM:

You are very lucky.

I've made the mistake of walking out the back door of a theatre when the CO2 guy was releasing gas out of a tank and had similar symptoms that you describe. Luckily I was outside.

Posted by Frank Cox (Member # 6258) on 04-20-2017, 10:47 PM:

I make it a habit to turn off the valve on top of the CO2 tank every night when the show is over and turn it on again before opening the door the following night.

Aside from the safety issue, it saves a lot of CO2 over the course of time since those tanks, regulators and connections to the machine are never 100% sealed so you always have a tiny leak unless you close the valve on the tank. There's no need for it to be open unless the machine is in use, and you don't walk in to find an empty tank that you just changed the day before, either.

Posted by Randy Stankey (Member # 64) on 04-20-2017, 11:02 PM:

I was taught to completely backseat the knob when opening the valve on any tank of gas. If you don't, gas can leak out around the valve stem.

BTW: Even if the atmosphere is only 20% saturated with CO2, an average human can only withstand 90 seconds to two minutes before feeling the effects. Any longer than that, the person will likely lose consciousness and be dead or brain damaged in five minutes.

At the place where I work there are several large tanks of liquid nitrogen that supply the Inert Gas Soldering machines. Those tanks are set up to vent excess pressure when the temperature changes. Even though I know that the building is very well ventilated it still makes me freak out every time I hear the pop-offs let loose.

Posted by Mike Blakesley (Member # 26) on 04-21-2017, 01:08 AM:

Randy - by "backseat," does that mean open the valve completely till it stops? I was taught the same thing.

Posted by Marcel Birgelen (Member # 6801) on 04-21-2017, 07:46 AM:

The topic title reads like something from a horror story. [Wink]

It's something still largely unknown, but CO2 in a small space can be quite deadly indeed. It's also odorless. Fortunately, nothing bad happened to you or anyone else.

You might remember Apollo 13. One of the biggest concerns for them also was the build-up of CO2 in a small space.

CO2 is heavier than oxygen and actually even displaces it in high concentrations and has a tendency to remain "stuck" in basements, when there's no active ventilation. But even with active ventilation, I doubt it will be sufficient in the unlikely event a large cylinder springs a leak.

I also have a rather large CO2 bottle in the basement and reading this it reminds me of the potential danger. Maybe it's wise to install some kind of gas detector. Unfortunately most of the simple smoke-detector style gas detectors are only suited for CO and not CO2.

Posted by Frank Angel (Member # 248) on 04-21-2017, 07:54 AM:

Geez Mike -- close call. Our tanks and syrup boxes are all in a closet-size space with hells-little ventilation. I have no idea at the moment what the concessions youngins do with the tanks at the end of the night, but I sure will find out. Also in that closet is the video system that plays promos on the video kiosks in the lobby. That means House Managers and ushers are in that small space for extended periods futzing with the equipment.

So what you are saying is that the tanks have the potential to off-gas if the valves are left open, even if there is no obvious malfunction (o-ring failing, seals deteriorating, etc)? If that is the case, we definitely will require full shut-off when we close.

Posted by Randy Stankey (Member # 64) on 04-21-2017, 12:06 PM:

quote: Mike Blakesley
Randy - by "backseat," does that mean open the valve completely till it stops? I was taught the same thing.

Yes, exactly. [Smile]

It was an old, hard boiled guy who was teaching me how to use a cutting torch. "Backseat" was his word. I took him for granted.

Posted by Dave Bird (Member # 490) on 04-21-2017, 12:10 PM:

Whew! This is the kind of thing people have never even heard of. A few years ago up here in the BC mountains, a guy went to check water samples as part of routine monitoring at a closed mine. He didn't return, fellow staffer went and saw him in this little covered well shack lying on the floor and he dropped. First paramedic and then second paramedic, same thing. Their instinct was to jump in and help, but all four were dead nearly instantly. Lots of iron in the ground, small unventilated space, there was just zero oxygen in there.

Posted by Mike Blakesley (Member # 26) on 04-21-2017, 12:35 PM:

This makes me wonder if maybe the problem was that when I had changed the tank the previous time, I failed to "backseat" the valve all the way. It's something I always do, but could have gotten in a hurry.

The only time anybody ever goes into this space is to change soda tanks, or to pick letters for the marquee. I do remember the tank on the line was a fairly new one - I'd probably changed it three or four days previous, and no one had been in that room since then.

If me sharing this helps one person down the road avoid a problem, then it was worth it! [thumbsup]

Posted by Frank Cox (Member # 6258) on 04-21-2017, 12:46 PM:

quote: Frank Angel
So what you are saying is that the tanks have the potential to off-gas if the valves are left open, even if there is no obvious malfunction (o-ring failing, seals deteriorating, etc)?

They do indeed. It's far safer to close the valve on the tank when you're not using it than to leave it open. Think of all of the little connections where hose-meets-fitting between your tank and the machine and you can see where there's lots of potential for a small leak. Have you ever hooked up a new tank and come in the next day and found it empty? Guess what....

Posted by Marcel Birgelen (Member # 6801) on 04-21-2017, 06:37 PM:

Maybe it's an idea to use some remote controlled solenoid valve for those purposes? Especially when there's a lot of piping between the location of the CO2 tank and the soda fountain. You could even couple it to the power state of your machine. It would save you a trip to the tank storage room every time you start up or shut down. Something which is also easily forgotten.

I've decided for myself I'll hookup a CO2 meter to the building automation later on. There are seemingly no out-of-the-box CO2 detectors with alarm function available, at least not around here. Eventually, I'll try to get rid off the tank in the basement entirely and place it in a better ventilated environment. I was thinking about a sheltered location outside, but I'm not so sure the pressure regulator, other valves and O-rings like being exposed to those conditions.

Posted by Frank Cox (Member # 6258) on 04-21-2017, 06:41 PM:

quote: Marcel Birgelen
Maybe it's an idea to use some remote controlled solenoid valve for those purposes?

I wouldn't. Use the valve on the tank. It only takes 30 seconds to open and close it. I even keep a small rag laying on top of that valve so I don't cut my fingers on the valve handle when opening it and closing it.

Posted by Clint Koch (Member # 1179) on 04-21-2017, 09:44 PM:

quote..."My soda machine tried to kill me"... I am very happy that it was not successful in its attempt!

Posted by Buck Wilson (Member # 5885) on 04-21-2017, 10:23 PM:

My manager tells a similar story. Old 4 plex, the restrooms and the syrup closet were down in the basement. One day he found that a co2 line broke and drained the whole tank into the small basement. Customers still wanted to use the restrooms despite the absence of oxygen. Dummys....

Posted by Leo Enticknap (Member # 534) on 04-21-2017, 11:31 PM:

Firstly and most importantly, very relieved that Mike is OK, and very grateful that he posted this. Almost all of us have these cylinders in our theaters, and it's a timely reminder to be very careful when handling them.

I have a story that did not have such a good outcome, told to me by a former boss. When he was a trainee projectionist in the 1950s, he arrived for work mid-afternoon, to find his chief slumped over a seat in the auditorium, dead. Next to him was a 30-foot ladder on its side, and a smashed light bulb on the floor.

What almost certainly happened is that he'd come in a bit early, intending to replace a blown house light bulb in the main auditorium, and the ladder had gone over while he was up it. The inquest later concluded that if someone else had been with him, they could have saved him just by putting him in the recovery position and calling an ambulance. He was killed by swelling to the brain going untreated for the best part of an hour.

Moral of the story: if you have to do a job that is even slightly dangerous - swapping out a xenon bulb, going up a ladder, you name it - don't do it alone and with no-one else to deliver first aid and/or summon help if an accident does happen.