Is it safe to use vinyl tubing as a breathing tube on a bong if no heat is applied to the tubing? - No heat is being directly applied to the tubing - The only purpose of the tubing is to direct the smoke out of one jar, into another jar, and then underwater/ice water/ice and also to direct the smoke from the final jar into the smokers mouth - I also have a version that only uses one jar instead of 3 and the tubing only serves as a way to carry the smoke out of the jar into the smokers mouth A while ago I had an idea to create a bong with multiple chambers using mason jars and tubes to connect them. So I finally ordered the parts and put it together yesterday and smoked out of it, and I gotta say it hits very smooth. However, I am concerned with the type of tubing that I used. I used a vinyl tubing and I read that it is dangerous to use if it is heated but heat is only applied to a glass bowl which connects to a glass downstem. The downstem is secured by a rubber grommet and the nearest vinyl is about a half inch away secured by another rubber grommet. Also the smoke travels down the downstem, through water and then up about an inch or two before it ever comes in contact with the tubing.