FromCarel LLC (Lancaster, PA), the Humicontrol gas-powered steam humidifier has 20% to 100% modulation with combustion efficiency at 94%. The unit is designed to detect excessive buildup of mineral scale on the heat exchanger and has a preheat circuit that allows the unit to respond to demand quickly. Features include a proportional air/gas valve with a double shutter, room-sealed combustion system, safety thermostat, and air pressure switch.