§ 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.