No damper shall be permitted in the smoke pipe or chimney from the device heated that may restrict to a dangerous extent the passage of fumes or gases. Ventilation shall be provided to prevent the accumulation of any trapped vapors below the combustion chamber. Complete instructions in regard to care and operation of the oil burning equipment shall be posted near the apparatus installed. The instruction sheet so posted shall include the specifications for the gravity and limiting flash point of oil suitable for use in the burner. All cards of instructions must be posted at time of installation. Near the entrance to the furnace room, and so located as to be convenient for use in emergency, there shall be provided a suitable hand extinguisher of approved type.