Because Isocyanates go to moisture , if you wear glasses and spray an iso product , check the inside of the lenses they will have more overspray then the out sides , I wear glasses and have to clean them after every job in my booth .
Its trying to get to the moisture in your eyes .
not all Iso products dry faster with humidity , because the moisture is trapped and has to evaporate too . slows the process down instead of speeds it up .