Krista,
Goto http://www.plasmafire.com
These are the best. They're $1,800. We refill our tank once a month, or up to 3-4 months depending on how often we use it and at what flow rate. I went to a welding supply shop and told them I was starting welding for fun and needed the smallest tank they had. (Don't tell them the real reason you want it, because you will need a perscription.) It costs me $18 to fill it. So it's cheap. These machines never need any maintenance & are guarenteed forever! You can give them to your kids and their kids & if it ever breaks down they will fix it. None have ever broke down in 50 years. These also come with everything you need to apply the ozone in all the different ways for all the different diseases. I got the beta unit because you can do the same thing the sauna does in the bath tub, so no need to buy the sauna. You can if you want. They're $2,300. Plus you can join Dr. Pressman's group at http://health.groups.yahoo.com/group/ozonetherapy
and search the archives and get a lot of answers & you can wrtie Dr. Pressman and he will answer your question too. He has all the answers to anything you could want to know. You should read the archives though, so you don't ask questions that have already been asked. He has also written two books on ozone and he will send them to you if you ask, or I can send them if you want.
Take Care,
Gaylen