Aprilaire is the leader in the heating ventilation and air conditioning (HVAC) accessories industry. All Aprilaire products undergo testing, engineering, research, product refinement and practical experience. Aprilaire furnace humidifier model 700 features truly automatic control. This device notes even the slightest change in outdoor temperature by using outdoor temperature sensor. In comparison to any other competitive units this device delivers up to 50% more moisture. This has an evaporation capacity of 0.75 gallons per hour. It humidifies tightly constructed homes up to 4200 sq ft in size. You can also operate the Aprilaire digital control in manual mode and still avail vital service, temperature and relative humidity.