May is the month you’ll most commonly find dehumidifiers turned on for the season in Washington’s damp and moldy basements. “We have a lot of old houses and a lot of humidity, so dehumidifiers are very popular,” says home inspector Alan Beal, president of Mid-Atlantic Inspection Services. Homeowners keep them humming until muggy season ends in October, preventing basements from smelling musty and repelling mildew and even cockroaches, moths and other bugs.