Added sorbent helps filter out nuisance levels of ozone, organic vapors and acid gas irritants (less that OSHA PEL). Exhalation valve reduces hot-air build-up. Keeps workers cooler and more comfortable. Collapse-resistant Dura-Mesh® shell lasts longer so workers use fewer masks. Flame-retardants added to help decrease flammability of shell. Shaped for comfort with contour molded nose-bridge. Seals easily and comfortably without a metal noseband. Certified under NIOSH 42CFR84 to have filter efficiency level of 95% or greater against particulate aerosols free of oil. Sold 10 per box.