They use MIL-PRD-83282. It can become contaminated with water, either from the air or condensation. Typically it is tested before being placed in an aircraft an

They use MIL-PRD-83282. It can become contaminated with water, either from the air or condensation. Typically it is tested before being placed in an aircraft and it can be purified if particle or water content is too high. https://www.pall.com/content/dam/pall/aerospace-defense/literature-library/non-gated/white-paper/mil-prf-83282.pdf https://www.pall.com/content/dam/pall/aerospace-defense/lite...