The HEPA filter is a high-performance particle filter, with efficiency of up to 0.3 μm (up to 99.8%). These filters are designed and intended for air-conditioning filtration devices in clean rooms. The filters used in BLOCK devices are designed in E11, H13, H14 Purity Classes, they incorporate an aluminium frame. The filter frame is provided either with a sponge rubber seal or a gel-filled groove into which the sealing lip of the device is embedded. The filter can be provided with an anodised protective grill to prevent damage.