i work full time at a hospital and have access to this tubing. i can check with the respiratory dept. and find out what they're made of, and use that to find out if they're CO2 permeable. my guess is that they're the same as the clear vinyl tubing from the lfs (clear, non-silicone) for 2 reasons.
1. oxygen loss across the walls of the tubing will be minimal at a flow of 2-15 liters / minute with no real buildup of pressure on the line like there is in a CO2 rig. the holes in an oxygen cannula (part that goes in a person's nose) are about 1/8" in diameter, and allow pretty free flow of oxygen through the tube, whereas a CO2 line run into an airstone or a container of water is much tougher to push gas through (it's easier to blow through a straw in the air than in a glass of water). in any case, the gas would follow the path of least resistance out of the tube and into the person's nose well before it would start pressing on the walls of the tube hard enough to squeeze between molecules of the tube and out into the room.
2. price. the tubing we all buy at petco, petsmart, lfs, wal-mart, big als is most likely the cheapest thing aquarium supply companies can get their hands on that will push a gas into a liquid and not foul the water. the same is true of oxygen tubing. if it does the job and doesn't hurt anything, why spend more money? i'm not saying that research and development aren't involved in O2 tubing, but when it comes to hospitals buying the stuff in bulk, the best price is usually the guy with the cheapest supply and the simplest product.
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