Abstract: A humidifier has a supply of water suspended on a pole above a patient which supplies water through a removable drop counter of magnetically actuated ball valve to a microporous tube mounted in but mechanically separated from a ventilating line between a ventilator and the patient. The water is heated in the microporous tube to create a vapor pressure sufficient to cause water vapor but substantially no liquid water to pass through the tube into the ventilating line. Electrically energized controls are provided to obviate maloperation and to maintain safe operating conditions including maintaining safe temperature conditions, and prevention of excess water entering the ventilation line by counting the drops of water passing through the bold valve, and closing the ball valve if the count rate is outside desired count rates and power or the monitoring equipment fails.