The factory housing is mostly sealed. It has breather vents. I think they use something like goretex membranes to allow airflow and moisture to escape but block water or dust intrusion. But it's not really open to the environment. Normal air exchange is limited to the heating and cooling expansion contraction. If it's not condensation becomes a problem. And sometimes they end up being dunked in water if you're going off road with them. You can't easily clean the inside so keeping it clean and free of moisture and dust is important for long term use.
EDIT: I found a picture of what the inside of one supposedly from a Toyota looks like. It appears to just be some small pore open cell foam as the filter material inside the vent cap.
![]()
that's great info thanks for that
so stock the 4runner headlight has some passive airflow built into it
the lasfit bulbs use that system to cool their led bulbs, i would think in extreme conditions those plugs would get clogged due to air actually being positively forced through them