Whether circle contact lenses are safe depends on where you get them from. If you get them from your doctor then they are safe. If it's online purchasing then make sure you get a good site. Any site that would sell you lenses without an Rx is a shady site. But you should only wear them up to 8 hours one day because they cover the whites of your eyes which take in oxygen to breath. Risk of infection is farely low to none if you take care of your eyes and your contacts.
Personally, I think circle contacts lenses are quite safe if you pay attention to these following things. Firstly, remember to buy them from formal glasses stores under the help of the professional technician. Secondly, you need to wear them correctly, as the technicians have told you. You'd better not wear the contacts for too long. Leave some time for your eye' rest and keep them moist with the eye drops. Thirdly, do keep clean. Make sure your hands are clean before wearing the contacts and wash the lenses with cleaner each time after you wear them. at last, you should also pay attention to some dangerous situation. For example, keep yourself away from fire and very hot temperature when you're wearing contacts. If you do so, the circle contacts lenses will definitely not cause any harm to your eyes.