If the structure which has been fumigated has an attic or if the area underneath such structure is accessible to inspection for purposes of structural pest control, the registered company which performed the fumigation shall, immediately upon completion, post in the attic, immediately adjacent to the entrance thereto, or in the area underneath the structure, immediately adjacent to the main entrance vent thereof, or in both of such places if the structure has an attic and an accessible underarea, a durable sign not less than five inches by seven inches in size stating the name of the registered company, the date of fumigation, and the type of fumigant used.