Seeking a superior air purifier replacement filter, we looked to a manufacturer in Holland for a F8-rated filter, made by CAMFIL FARR and compliant with EN799 and rated by EUROVENT – globally recognised as the leading professional organisaton for overseeing the development of heating and ventilation systems worldwide. View the rating. These deep-pleated filters have a wider filtration surface than most filters used in New Zealand HRV systems, and are manufactured from continuously spun glass fibres with a progressive thickness, enabling dust to be collected across the whole surface area.