I did an experiment several years ago, to check how much CO2 leaks from silicone tubing, which had been said to be unsuitable for CO2. I bought a cheap roll of silicone (blue) tubing from PertSmart. I connected the whole roll of tubing to the CO2 regulator, placed it in a 2 quart container of water, and measured the pH of that water for an hour or two, for increasingly high CO2 pressures. Any CO2 leaking through the tube walls would dissolve in the water and the pH would drop at least a little due to that CO2. I had no pH change at all. I also watched for bubbles from the tubing, and saw none. I shut off the CO2 and watched for a pressure drop, and got none. My conclusion was that silicone tubing works fine for our CO2 systems, but would not work as a CO2 diffuser, which I was really hoping to demonstrate.
I always found that my vinyl tubing would slowly harden, while the silicone tubing didn't. That, plus the difficulty in connecting special vinyl CO2 tubing, convinced me to use only silicone tubing.