Air filters are a very important and significant component of air handling units. They are important to the air handling system with respect to functionality and energy aspects. The most important function of an air filter is to clean the air, protect the air handling equipment and create a clean indoor air quality. They also have to fulfil demands and criteria so that the product fit into the air handling installation. Energy conservation in design and operation is of high importance. Part of the public enquiry specifications objective is to also keep the energy consumption at a low level. However, it goes without saying that the filtration efficiency of the filter must never be lowered on behalf of the energy saving. The combination of an efficient particulate air filter, IAQ requirements and low energy consumption put the focus on the correct specification and validation of air filters. For this purpose Eurovent has developed a recommendation covering the most important parameters and demands that should be taken into consideration when writing a valid requisition, public tender or enquiry for air filters. It is important that customers are provided with a tool enabling them to compare the different quotations and filter brands in an unbiased way. This is the English version of the document.