Samples representing state-of-the-art 3.8-μm laser optical components were sequentially exposed to potentially harmful ingredients of an airborne-operating environment and tested for degradation after each exposure. Two enhanced-reflection-coated mirror designs, Mo(substrate)/Ag/ZnS/(ThF₄/ZnS)⁴ and Si(substrate)/Ag/Si/(Al₂O₃/Si)⁴, were studied, along with the antireflection-coated window designs, CaF₂ (substrate)/PbF₄/ThF₄/PbF₄ and ZnSe(substrate)/ZnSe/ThF₄/ZnSe. Samples were exposed to controlled moderate doses of (1) methanol or acetone applied as cleaning solvents, (2) simulated atmospheric solar radiation at 6-km altitude, (3) 100% humidity ambient, and (4) an ambient containing 10% HF gas. Testing consisted of the following measurements at 3.8 μm: multithreshold pulsed damage profiles, absorptance, scattering, and absolute reflectance/transmission. While cleaning solvents and sunlight generally produce a reduction of thresholds for uniform damage, the influence of humidity and HF is more subtle, resulting in a significant increase in some cases. The windows respond differently than the mirrors, a result that is evidently related to an observed difference in the dominant damage characteristics. Optical characteristics do not correlate well with damage thresholds, suggesting that modification of thermal or other material properties plays a more important role.