Hi Cyane
The Nature Kleen IMO is the best unit on the market for the money for simple water ozonation.Although the warranty states 1 year, someone else on this forum posted that they have had theirs for three years used daily with no problems. Myself, I have used the same ozone cell that is in the Nature Kleen for over five years running 24/7 on my hot tub. No problems. Very reliable. In the same amount of time one would go through about six or eight Enalys if they ran 24/7.

As for the model 308, that is the only color available. As far as personal use beyond a year, I have no experience with that, but a friend of mine has run one full blast 24/7 for 4 months now without any problems. I believe it will greatly outlive it's one year warranty, especially if routine maintenance is done. Any air ozonator will require routine cleaning.

Start off slowly with the ozone output and get used to each new level. The nose is a very lazy sense and will get used to the ozone easily. Within about 1/2 hour you will typically not smell ozone any longer, even if the level is quite high. The trick to get an idea how strong the ozone is in a room is to leave the room , go outdoors for a few minutes, then return to the room. If ozone can be just detected but not too stong,then this level is likely OK and will not cause respiratory problems. If it is strong smelling, it probably is too much for a newbie, so turn it down a bit.I would start with the machine on minimum at night in the bedroom and just see how you feel in the morning. Clear signs of overexposure to ozone are dry cough, irritable lungs, tightness in chest, dry sinuses, and perhaps even mucous discharge. This is just the body releasing the toxins from the tissues, challenging the body to eliminate them. If you experience any of these signs, turn the unit down until your body gets used to the level you're at. This could take weeks of exposure depending on how many toxins are in the home and how well your body adapts to the ozone level.It is my belief that even high levels of ozone will cause no permanent damage. It may be very uncomfortable for a short period of time, but the discomfort goes away.Should you find you've overdone it, a 1000mg dose of vitamin C will help ease the symptoms.
Just use good common sense and be aware of the signs of overexposure.
Hope this helps. All the Blessings of the Season to you and yours. I will be away until about the 28th, starting tomorrow.
Cheers,
paul

i bought a nature kleen about three years ago, i still use it almost everyday. it still works as well as the day i bought and i have never had any problems with it. ozone output still seems as strong as it was originally. i don't think you can go wrong with it.