location of bath ventilation fan

i'm going to add a ventilation fan to my bathroom when i add a shower to the tub.
the tub/shower is enclosed on 3 1/2 sides with walls that go all the way to the ceiling. the bathroom is about 6 x 12.

the pipes to the upstairs bath are in the way of mounting the fan in the tub/shower ceiling. i suppose i could move them if needed.

but i'd rather just mount the fan in the ceiling outside the tub/shower, or even on the exterior wall.
but i'm worried that the moist air won't get drawn out of the shower/tub area - especially if the curtain is closed - unless the fan is in there.

comments please

how about a soffit over the tub to have room for the fan.

The better place for the fan is in front of the tub, and centered to the walls.

If the toilet is setting by the tub, it would center with the toilet, and then center to the walls front and back.

If you are thinking of a fan light combo, this is also the best spot for the light.
It makes for good reading on the throne, and lights the tub well without being overhead while you stand in the shower.

I'm not a fan of any electrical devices in the shower.

The typical installation is just as described by Terry. Putting the fan over the shower/tub area requires a GFCI circuit as well as a fan rated for moist environments..... which the typical fan is not....