A substantial feature of the air filter, besides the efficiency of particle separation, is its flow resistance which directly translates into an energy consumption. This parame- ter plays an increasingly important role.

Due to rising Ecodesign requirements for ventilation equipment, pressure drop over filters pertains a significant share of the overall pressure drop in HVAC systems. It has a crucial impact on the total energy consumed by mechanical ventilation. Energy efficiency links the amount of energy required (effort) to the particle filtration efficiency of the filter (benefit).  Understanding this energy efficiency is even more relevant when acknowledging that many end users are not aware of differences in energy consumption related to various filters offering an equal filtration efficiency performance.