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Cold air holds very little water. When it comes inside and gets heated, its relative humidity drops, often to 20% or lower in January. That’s drier than most deserts, and it’s why your lips crack, your skin itches, and you wake up with a dry throat.
The EPA recommends keeping indoor humidity between 30% and 50%. Below 30%, you feel it. Above 50%, condensation forms on windows and mold has a chance to grow.
Check before you buy
Put a $15 hygrometer in the room for a day. If it reads above 35%, you don’t need a humidifier at all; a glass of water by the bed won’t change much either way. If it reads in the 20s, a humidifier will make a real difference.
Honeywell Evaporative Humidifier
Wicks water into the air without white dust. Can't over-humidify a room.
Check price on Amazon: Honeywell Evaporative Humidifier (opens in a new tab)Levoit Ultrasonic Cool Mist Humidifier
Near-silent, with a built-in humidistat. Best for a bedroom.
Check price on Amazon: Levoit Ultrasonic Cool Mist Humidifier (opens in a new tab)Vicks Warm Mist Humidifier
Boils the water, so the mist is clean. Good where tap water is hard.
Check price on Amazon: Vicks Warm Mist Humidifier (opens in a new tab)ThermoPro TP50 Hygrometer
Under $15. Tells you if the room is actually dry before you buy anything else.
Check price on Amazon: ThermoPro TP50 Hygrometer (opens in a new tab)Which type for which room
Evaporative humidifiers blow air through a wet wick. They can’t push humidity past what the air will take, so they’re hard to overdo, and they leave no white dust. A good pick for a large room. The wick needs replacing every month or two.
Ultrasonic cool-mist models are nearly silent, which matters in a bedroom. Use distilled water if your tap water is hard, or a fine white dust settles on the furniture.
Warm-mist models boil the water first, so the mist is clean even with hard water. They use more power and the water gets hot, so keep them away from kids and pets.
Keep it clean
A humidifier with standing water grows bacteria within days. Empty it daily, rinse the tank, and clean it with white vinegar once a week. Set it to hold 40–45%, not to run flat out.