In the context of increasing energy prices and the imperative of reducing CO2 emissions, the energy consumption related to air filters has become the focus of attention. Air filters used for general ventilation are tested and classified according to their particle efficiencies, especially with respect to the removal of particulate matter, in accordance with the ISO 16890 series of standards. The aim of this guideline is to define a method of air filter classification with regard to energy-efficient operation, to give the user of air filters guidance for the filter selection. In a nutshell the purpose of this recommendation is to 1. Define energy efficiency of air filters for general ventilation purposes, 2. Define energy efficiency evaluation methods, 3. Implement the ISO 16890 classification and testing methods in place of EN 779. This document is available in English.