Bathroom/Mikvah/Skin processing plant:
A bathroom or Mikveh is exempt from having a Mezuzah being that they were not made for an honorable form of dwelling. Thus they should not have a Mezuzah placed on their doors even if the Mezuzah will be covered.
Does the lounge of a Mikveh, or the room in which the payment is collected, require a Mezuzah?
Is a Sauna or steam room obligated in a Mezuzah?
Does a slaughtering house require a Mezuzah?
The area in which the animals are slaughtered do not require a Mezuzah unless the area leads to an a room of dwelling.
Does a room require a Mezuzah if its entrance is through a bathroom?
The door of that room is to have a Mezuzah placed inside, behind the door. The door which enters into the bathroom remains exempt from a Mezuzah.