Transmissive and reflective optics for high power CO2 lasers were exposed to define relative humidities and temperatures. Degradation effects were investigated by means of absorptance, reflectance, laser-induced damage threshold measurements and microscopic inspection. The LIDT measurements were performed in the short and long-pulse regime involving different test routines as 1 on 1, S on 1 and R on 1. For distinct coatings, microscopic investigation reveal a size-increase of the nodular defects. This increase results in a reduction of the defect induced LIDT, while the absorptance and reflectance remain unchanged. Alkali-halide components show an intensity-dependent laser-induced conditioning effect. This effect is analyzed with respect to different environmental parameters.