Performed maintenance on a furnace and humidifier. When I arrived, the humidifier was operating well however the drain hose was disconnected and leaking water on the floor. I reattached it and cleaned up the water. I then checked the entire system and everything checked out except for the static pressure. Homeowner is already aware of this. When I checked the evaporator coil, there was some microbial growth that had started to form. I took pictures and let the homeowner know that a UV light with germicidal unit is highly recommended in the future to kill this growth and keep the air clean.