The Odyssey has what ÖKO calls Level 1 and Level 2 filters. The first is just like your Brita carbon filter, designed for everyday use with tap water. It removes chlorine taste and odor, providing cleaner tasting water on the go. The Level 2 version is a more serious filter that can rip bacteria, cysts and other contaminants out of the water. ÖKO says that the Level 2 filter is designed to travel and clean water in more than 140 countries around the world, where water conditions are not as clean and reliable as they are in the first world.