AutoFlo 40S is a power humidifier designed for use with gas or oil-fired, forced-air or gravity furnaces. It operates on the forced-air evaporative principle, adding moisture to warm air ducts to increase indoor relative humidity. The AutoFlo 40S is equipped with a solenoid valve to regulate water flow and an evaporative media pad to distribute moisture evenly. It features a water pan with a float valve assembly for automatic water level control and a drain connection for overflow prevention.