We ran a humidifier 24/7 in the living area (still do, actually). And the BiPAP always was humidified. There's an additive you can buy on line to keep mold from building up in the room humidifier (and of course, you clean it!) To me, to "purify" without humidification wouldn't make a lot of sense given the role of dryness. But whatever someone is comfortable with.