RH = Relative humidity; the quantity of drinking water vapor while in the air in comparison to the level of water vapor the air could hold at saturation. It helps prevent backdrafts, which might occur when negative tension builds up in your house. Backdrafts can herald cold air or pollutants, https://aircontroldampersforhotcl68901.blog2news.com/37292897/top-guidelines-of-air-control-dampers-for-hot-climates