Environmental armor Mark II is an advanced version of the regular environmental armor, developed for use in heavily contaminated environments, and is prized in the wasteland for its ability to protect against biological threats.
This armor affords the wearer 90% protection against harmful airborne agents and radiation.
Eastern Brotherhood of Steel Knights are sometimes dressed in environmental armor. This protects them against radiation, chemical and biowarfare agents. Of course, it also helps with the brahmin smell.