Eurovent 4.5 and Eurovent 4.4 are two distinct standards developed by Eurovent, a European association of air conditioning and refrigeration manufacturers. Eurovent 4.5 is designed for primary and secondary filters, while Eurovent 4.4 is specifically tailored for high-efficiency filters. The main difference lies in the filter efficiency classification, with Eurovent 4.5 focusing on lower to medium efficiency filters and Eurovent 4.4 catering to higher efficiency filters. This distinction enables manufacturers to design and test filters according to specific application requirements.