The first high colonic I had was on a Libbe open system. This is a fiberglass table with a cut out in the middle. The speculem comes through the hole. There is a ventilation system so there is no odor. Do a search on Libbe and you'll see what the table looks like.
My second high colonic was on a closed Detolo system. This system uses a much larger speculim and the water tube and waste tube combine at the speculem which has a one way valve to keep the waste and water from mixing. The main difference is the size of the speculem. Do a search on Detolo to see what a closed system looks like.
The main difference to me is the speculem size. I prefer the open system with the small one. Some people say the closed system works better. Try both and you be the judge.