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Technical Q&A with Lennard Zinn: CO2 tales and comments

By Lennard Zinn

Can this happen to you?

Can this happen to you?


Dear readers,
I’ve enjoyed the recent exchange on CO2 cartridges, and judging by the volume of lighthearted mail I’ve received on it, so have a lot of you. I thought we’d thoroughly covered all of the technical aspects of it to the point that no more needed to be said.

And clearly my answer about an aero vs. round-tube road frame stirred up a lot of interest, so I’d like to return to that subject, and even before that I’d like to return to the subject of rim corrosion from tire sealants that we just literally and figuratively scratched the surface of (got any experiences about this you want to relate before next week?).

However, there were a couple of questions left hanging out there in last week’s column about inflation cartridges, specifically whether readers have had experience with either exploding beer or pop cans in cars or airplanes, or, more importantly, with exploding inflation cartridges. Some unspoken questions also remain about particularly negative experiences with the airlines and about some assertions of a reader that may have been inaccurate. And I got enough informative mail about these items that I do want to post a sample one of each. I think there is some more all of us can learn from these, so bear with me this one more week and then we’ll declare the CO2 horse officially dead. And of course plenty of you wrote that carrying a frame pump instead of cartridges eliminates the entire question.
Thanks for all of your mail.

Dear Lennard,
Just read the forum on CO2 cartridges and wanted to let you know that my wife and I had a Big Air explode in our car last summer. Not sure what caused it to explode, but it was in my wife’s saddle back at the time of explosion. It completely decimated the saddle bag. Tools were spread all over the car. In fact, I just found the tire irons under the passenger side seat.

It appears that the bottom of the canister failed.

Dear Lennard,
Back in my younger days when I was working at the local Pennsylvania golf course in the summers (I didn’t discover road biking until much later in life), I accidentally left a can of Coke on the small shelf under the glove box of my car.

The can survived my day at work intact. It wasn’t until I was driving home that it exploded. Of course the top of the can just happened to be aimed at the driver’s seat. The simultaneous loud bang/pop and drenching initially scared the !@# out of me 😉 No harm done, but it sure made a mess. Thought a little light-hearted story might be of interest.

Keep the interesting discussions coming.

Dear Lennard,
I learned the airline CO2 cartridge ban the hard way in January 2009. My wife and I were unceremoniously removed from our return flight from Tampa to Denver. A scan of my bike box showed cartridges; I was already on the plane when the airline tried to page me.

My 3.5 hour direct flight home turned into a 16 hour trip on another set of flights. The airline (United) showed me printed rules on their brochure (the font size is about 3 pt); they were actually quite helpful.

Next time I fly with my bike, I’ll just take a pump.

Dear Lennard,
I love the convenience of CO2 cartridges. I’ve flown for years taking my road bike and related equipment on various airline carriers domestically and internationally. I have never declared the contents of my on-the-bike small packs, include CO2 cartridges. On domestic flights, I have never been told CO2 cartridges were prohibited cargo and I have never had a problem transporting them within my bike transport container.

But when flying out of Brussels, Belgium, returning to the states after the 2005 Ronde van Vlanderen Golden Bike event on an American airline with two teammates, I was informed at the check-in counter that many prohibited items, including CO2 cartridges, must not be transported in our luggage.

Because I knew the CO2 cartridges I had within my bike container had passed without objection through security on my previous flights and because I did not want to unpack my densely packed bike container, I decided to do nothing. We cleared security and settled into our boarding area seats to wait for departure.

One-half hour before departure, my name was announced on the public address system and I was directed to approach the boarding counter. I was met by gun toting BIA security agents (they carry automatic weapons in the Brussels airport) who escorted me through a warren of back area hallways to a brightly lit, windowless small room with two agents waiting for me. After seating me in a hard backed aluminum chair, I was interrogated at length as to my travel plans and the contents of my luggage.

The final question asked was whether I had any CO2 cartridges in my bike container. I admitted the apparently obvious fact and the container was forthwith rolled into the room. I was instructed to find all cartridges while the agents looked on with steely eyes. I glanced at my watch; my flight was scheduled to depart in 10 minutes. Within two or so minutes, I found two cartridges and handed them over to an agent. However, I couldn’t put my hands on a third cartridge I had packed somewhere in the container. I didn’t mention it. I passed the cartridges to an agent and said, “That’s it.”

They looked satisfied.

I was escorted at a snail-like pace to the boarding gate area and entered the airplane as the last passenger before the door was closed and we left. I wondered whether I’d ever see my bike again. Several hours later, we landed at O’Hare and my luggage was waiting for me by the time we got to baggage claim. Once home, I found the third cartridge well hidden in my seat post.

Moral of the story: If they say don’t do it, don’t do it.

Dear Lennard,
It’s scary when people have a little bit of knowledge on something, but no real expertise. For example, your reader Mark’s comments are full of inaccuracies.

First of all, there are “natural” sources of CO2, obtained via combustion of limestone, for example. But there are many ways of obtaining CO2 by other means, including capturing it from the process that produces ethanol from corn. Furthermore, there are many “manufacturers” of CO2 in the U.S., which I won’t specifically point out because I don’t represent or want to misrepresent any of those companies. Suffice to say it is unreasonable to think manufacturing CO2 off-shore and importing it into the U.S. could be economically viable and that there isn’t the technology today to mitigate any EPA concerns.

While this doesn’t have much to do with CO2 cartridges and their inherent safety concerns in aircraft, inaccuracies from Mark’s comments lead to take his overall comments with a spoonful of salt.

I work in the aircraft industry on the design end. I can tell you that anything that goes into the design of an aircraft or equipment that is integral to the operation of the aircraft is strenuously analyzed and tested beyond what most sensible people find reasonable.

With that said, the CO2 cartridges which inflate flotation devices may well contain the exact same formula as what we inflate our bike tires with but they have to be certified by Federal and International aviation governing bodies, which means they have to show that they meet certain standards through design, analysis, and testing which all has to be properly documented.

Now consider that our CO2 cartridges that we use to air up bike tires have not been through this level of design/analysis/testing…and if they have they haven’t been documented and certified by the FAA. And because of this they are seen as compressed gas containers which can be seen as being potentially harmful by the FAA.

So yeah, you’re going to have to leave those at the security gate with your pocket knives, nose hair trimmers and oversized bottles of cologne. They would likely be completely fine, but the point is they haven’t been certified.

As a point of reference, another engineer I knew spent an entire four months of his life trying to get a DVD player FAA certified to go on a certain large un-named executive passenger aircraft that is operated by the U.S. Air Force. Granted there was nothing particularly unusual about this DVD player. It just had to go through the proper channels before it could be integrated into the aircraft.

Dear Lennard,
I would like to respond regarding the comments by one of your readers (Mark).

The little rubber bumper on the bottom of the shaving cream can is not a relief valve. It is where the container is filled with propellant, which is typically a propane or butane blend. The shaving cream cannot be mixed with the propellant so there is either a “piston” or “bag separating the shaving cream from the propellant. Note that some shaving creams can be mixed with the propellant and are filled normally through the valve or under the crimped cup. There is no linkage between the rubber plug and a valve (thumb switch). About 25 percent of shaving cream cans are filled from the bottom. The vast majority of aerosol cans are filled with propellant under the crimped cup or directly through the valve. In order to meet transportations standards, aerosol cans are subject to a hot water bath to do a proof test on each aerosol containers. Aerosol containers are not allowed in the U.S. without proof of this testing. This is covered by U.S. Department of Transportation standards for shipping.

The only aerosol containers with a relief valve are containers with products that would spoil within the hot water temperature bath. This is typically whipped cream. Examination of a whipped cream aerosol container will reveal a set of cut marks on the upper, outer chime (crimped edge). These cuts create a relieve valve that will slowly leak well before the container will burst.

I find Mark’s response does not meet any scientific scrutiny. Containers will explode, not detonate. No one manufactures CO2 in the U.S.? Where do all the bottles for CO2 lasers come from? I can call the local welding shops and get many bottles of CO2. I have done many filling tests with CO2. It is the main propellant for brake cleaners. Planters Peanuts have a drop of liquid CO2 dropped in them before they are sealed. This is a method to displace the oxygen from the container and keep the stored product fresh. This is common in the food packaging industries. Your lettuce in the bag is fresh in the store because there is no oxygen in the bag. It will wilt quickly as soon as it is opened. This allows substantial increase in product storage time. The EPA allows this. The stuff in these cartridges is CO2 gas under high pressure and I am fine with it.

Mark says that “there is no way to get CO2 from ‘natural sources’ or ‘volcanic sources’ CO2 in these cartridges are completely man made/ manufactured.”

This reminds of the reward some British scientists offered for any example of an “unnatural” substance.

Technical writer Lennard Zinn is a frame builder (www.zinncycles.com), a former U.S. national team rider and author of numerous books on bikes and bike maintenance including the pair of successful maintenance guides “Zinn and the Art of Mountain Bike Maintenance” – now available also on DVD, and “Zinn and the Art of Road Bike Maintenance,” as well as “Zinn and the Art of Triathlon Bikes” and “Zinn’s Cycling Primer: Maintenance Tips and Skill Building for Cyclists.”

Zinn’s regular column is devoted to addressing readers’ technical questions about bikes, their care and feeding and how we as riders can use them as comfortably and efficiently as possible. Readers can send brief technical questions directly to Zinn. Zinn’s column appears here each Tuesday.