The Dr. PTAC option is available in Islandaire’s EZ Series DR product line and in the EZ Series VR (vertical unit). The Dr. PTAC module is designed to constantly bring in fresh air into the living space. When the relative humidity level outside reaches a range of 40 percent to 100 percent, the additional compressor is engaged to condition the fresh air as it enters the room. The primary stage conditions room air and tempers the air to acceptable air quality levels. The secondary stage brings in conditioned outside air to compensate for toilet exhaust and room occupancy and continuously pressurizes the room.