Pure Australian Tea Tree Oil in a specially formulated Gelair gel matrix block. The Gelair Air Conditioning Block is specifically designed to provide controlled and sustained release of Pure Tea Tree Oil vapor in high volume, high flow areas such as the Air Handling Unit (AHU) of an air conditioning system. Gelair Air Conditioning Blocks stop the spread of invisible mold, bacteria and viruses. No installation of equipment or training is required. A natural product with no maintenance or energy costs.