The double doors into my darkroom have 1" gaps at the floor, thus letting in enough light that you can see the floor quite well once your eyes adjust. I have seen no evidence of fogging from this, and in fact the darkroom itself has been in use for 30+ years. The double doors have a kind of collimating effect, there is almost no light coming up off the floor, though it can make your shoes glow.
For tray dev of IR and fast films, I put a lid on my trays.
Bear in mind that the dark-adjusted eyes have rather spectacular sensitivity. You can have unmeterably low levels of light, maybe 10-20 stops below what you can meter, and still see around quite well. IIRC the dark-adjusted eye can see the light from single candle at one mile distance.... quite near single-photon sensitivity.