For Meridiano 87, the double air filtering air is one that not only meets international standards to be certified as Grade E (What is Air Grade E?) if not, makes a further filtering process that can be used on rolls ready for use with gases with a high content of oxygen. This is also known by its English acronym OCA or Oxygen Compatible Air. In the case of meridian double air filter 87 additionally meets the regulations for air USP Medical Grade..
The Filtered differs mostly outdoor grade E for its extremely low level of oil pollution as shown in the tables below