How much moisture does a vent-free appliance put out?
The amount of moisture is dependent on the gas Btu input. A 100,000 Btu/hr gas input produces about a gallon of water per hour. A 25,000 Btu input heater would produce about a quart of water as vapor per hour. It is important to keep this issue in perspective. When a typical consumer sees condensation on a window, it does not trigger an immediate alarm regarding allergenic organism growth or structural damage. The relative humidity in residential indoor air results from many contributing factors: cooking, showers, dishwashing, humidifiers, etc. The American Society of Heating, Refrigerating, and Air Conditioning Engineers (ASHRAE) recommends a maximum relative humidity value of 60 percent for human comfort. The AGAR research project (see Section B, Safety Issues, Number 5, above) demonstrated that, even under “worst case” conditions, the highest relative humidity produced by vent-free gas heating products was only 49 percent, well below the recognized comfort level of 60 percent. In fa
