Some information about the procedures for changing the absolute filters in air conditioning systems.

The replacement of the absolute filter is normally performed when the pressure drop of the filter element reaches the manufacturer's recommended value. But often the elements are changed in periodic checks (each company has a frequency that can be every 6 months up to a year), in which the conditions of tightness can be checked: - the filter medium; - the filter element and structure couplings; - the absolute filter receiving structure. These periodic checks are important because the absolute filter has an efficiency of 99.97% for particles of 0.3 micron, and our eye can only see particles larger than 25.0 microns, so the penetration tests DOP, PAO and Particle counting are the methods that ensure that the filter system plus structure are in accordance with the specified.