Section 306. Service of notices and orders

Every notice or order issued by
  the  department  relative  to a premises shall be served at least thirty
  days before the time for compliance therewith. It  shall  be  sufficient
  service  of  a  departmental  notice  or  order,  if  it  is posted in a
  conspicuous place upon the premises affected and a copy thereof  mailed,
  on  the  same  day it is posted, to the person to whom it is directed at
  the address filed by him in the department, and, if his address  is  not
  so filed in the department, then in such case, such notice shall be sent
  by registered mail to his last known address or place of residence.