In mines partially rock-dusted or in mines that are required to start rock-dusting, haulage ways and parallel entries connected thereto by open crosscuts, shall be rock-dusted. Back entries shall be rock-dusted for at least 1,000 feet outby the junction with the first active entry. Inby this junction, the rooms, entries, and crosscuts, shall be rock-dusted. Rock-dusting shall be started at once and completed as herein provided, and the mine shall be rock-dusted as it develops and rock-dusting shall be maintained to the shaft bottom or entrance.