4.When we talk about class 0 this must refer to certain
parameters more specific and greater than level 1, we can
not call a filter a class 0 without specifying the quality it is
ISO 8573 2-4-2, has a concentration of particles per m3
according to each class 2 micron size, a pressurized dew
point (water in the air), 3 ° C, and a total oil concentration
less than 5 mg / m3 of air.