HEPA means High Efficiency Particulate Air (Arrestance) according to a number of Standards:
EN1822 classify Filter media "H" Class (High Efficiency Particulate Air) and "U" Class (Ultra- High Efficiency Particulate Air). H Class Filter Media is of extremely high arrestance and can be utilised in Open Heavy Industrial environmental conditions but only with the controlled air flow and and efficient Precleaner Technology that will remove the debris from the incoming Air before loading he Filter Element / Media. Without a Precleaner or with extremes of Air Flow then the HEPA Filter will load and block very rapidly.Subsequently a U Class Media is neither practical or for that matter needed as it would load / block even more quickly.
The HEPA Filter Elements we use in our Q-CABAIR™ Quality Cabin Environmental Air System are >H13 / H14 Class and achieve the highest Arrestance Efficiency (pragmatically) of:
It is important to note that stating Filter Efficiencies / Classes of the Filter Element or Media- does not mean that the complete Cabin Environmental Air System is compliant