VDI-EE 3781 Blatt 5:2025-05

This expert recommendation applies to the discharge of diffuse emissions from channeled sources from installations not requiring a permit with a focus on combustion systems and from installations requiring a permit with infrequent emissions or installations requiring a permit with low emission mass flow rates, where adequate dilution of the waste gases can be ensured without undisturbed removal with the free airflow. Diffuse emissions from channelled sources within the meaning of this expert recommendation are channeled emissions that do not meet the requirements of standard VDI 3781 Part 4 for the undisturbed removal of waste gases with the free airflow. This expert recommendation for the discharge of infrequent emissions from installations requiring a permit only applies if sufficient protection against harmful effects on the environment is ensured and further precautions against harmful effects on the environment for the purposes of the Federal Immission Control Act (BImSchG) are not required in individual cases due to undisturbed waste gas discharge. This expert recommendation does not serve to determine the minimum height of the outlets of waste gas discharge systems to ensure the undisturbed removal of waste gases with the free airflow. Reference is made to the standard VDI 3781 Part 4. The standard VDI 3781 Part 4 describes the technical principles and requirements for the undisturbed removal of the waste gases with the free airflow and, under this prerequisite, also for the adequate dilution of the waste gases. It does not consider cases in which adequate dilution of the waste gases is already ensured without the prerequisite of undisturbed removal of the waste gases. The standard VDI 3781 Part 4 also does not take into account cases in which waste gases are only emitted within a few hours of the year. This means that the standard does not consider two relevant categories of waste gas discharge, that would be the diffuse discharge of low and the diffuse discharge of infrequent emissions from channelled sources. This expert recommendation closes this gap. The criteria for adequate dilution and infrequency described in this expert recommendation do not consider harmful environmental impacts from odour emissions.

07.060, 13.040.01, 91.060.40