 What is the best setting for my deal humidifier? No one can give me a simple answer. Whatever keeps the room from feeling like a fetted swamp, and ideally from being a cool dry tomb. I've heard that different settings would affect performance. Sure. If it is off, it won't work, and if the ideal humidity setting is close to what the real humidity is, it won't work. What settings should I avoid? Setting your ideal humidity level too low could wear out the dehumidifier because it is always running. I need the area less humid. If a dehumidifier isn't good enough, the problem may not be the dehumidifier's settings. There might be a water leak in the area. There's no leak from the washer or water softener. Maybe there's a foundation leak in the basement letting water trickle in. You blame the humidity in humidifier instead of looking for cracks in the basement. I can check for leaks. But what is the ideal humidity level? The ideal humidity level is around 35% to 45%. Higher than that encourages mold and bacteria to grow, while less than that can draw moisture out of furniture and make it crack. And be so dry that irritates your eyes and nose. But I definitely want to stop mold and bacteria growth. You can't stop it, but lowering the humidity levels will slow them down. I heard 50% is bad. Anything above 45% to 50% will start to damage materials long term, plus fuel the growth of dust mites, rot and everything else you don't want. They say water is life, and high humidity feeds everything. Except anything over 45% can make it stuffy to you and lead to heavy sweating. In that regard, high humidity can dehydrate you. It sounds like 40% is the ideal level for my dehumidifier then.