Reflector discs OTP are designed to reduce the loss of oil products when breathing valves are relieved of excess pressure in tanks with oil and oil products. The mechanism for reducing losses is that the OTP reflector disc, suspended under the mounting branch pipe of the breathing valve, does not allow the flow of air entering the reservoir to freely spread deep into the gas space, changes its direction from vertical to almost horizontal. Therefore, the mixing of the vapor-air mixture mainly occurs in the layers adjacent to the roof of the tank. The most saturated layers of the gas space, located at the surface of the product, almost do not participate in the process of convective mixing. In this way, the reflector disc reduces vapor concentration and evaporation losses.