Aprilaire 350 APRILAIRE HUMIDIFIER Brand new Aprilaire Humidifer 350. Self contained Aprilaire Humidifer designed to fit in within closets, basements and heated crawl spaces. Evaporative capacity of 0.50 gallons per hour. Can be used in a home of up to 4,500 square feet.Fast shipping and low prices on Aprilaire Humidifer 350. Buy now!