Do I need special ventilation


You do not need any special ventilation for a steam room or steam shower. The steam will condense back to water and drain away. You can speed up this process by running the shower.

Most bathrooms have a vent extract outside the shower, which should be sufficient to remove any steam that escapes during use. If you are building a larger steam room with a particularly well-sealed door, a passive vent with screw cap inside the area will assist the steam circulation.