Efficiency grade is only the starting point when choosing a HEPA filter for an air purifier. Airflow path, installation space, target airflow and noise limits all affect filter resistance and dimensions.
Define the particle target and operating environment first, then confirm media efficiency, pleat spacing, filtration area and frame sealing. For combined purification designs, balance the resistance split between the HEPA stage and the carbon stage.
During sampling, record initial resistance, airflow characteristics and dust-loading trends. Use test data to judge whether the design meets the device requirements, rather than relying on a single efficiency figure.