30 CFR § 75.341
Direct-fired intake air heaters.
(a) If any system used to heat intake air malfunctions, the heaters
affected shall switch off automatically.
(b) Thermal overload devices shall protect the blower motor from
(c) The fuel supply shall turn off automatically if a flame-out
(d) Each heater shall be located or guarded to prevent contact by persons
and shall be equipped with a screen at the inlet to prevent combustible
materials from passing over the burner units.
(e) If intake air heaters use liquefied fuel systems--
(1) Hydrostatic relief valves installed on vaporizers and on storage
tanks shall be vented; and
(2) Fuel storage tanks shall be located or protected to prevent fuel
from leaking into the mine.
(f) Following any period of 8 hours or more during which a heater does
not operate, the heater and its associated components shall be examined
within its first hour of operation. Additionally, each heater and its
components shall be examined at least once each shift that the heater
operates. The examination shall include measurement of the carbon monoxide
concentration at the bottom of each shaft, slope, or in the drift opening
where air is being heated. The measurements shall be taken by a person
designated by the operator or by a carbon monoxide sensor that is calibrated
with a known concentration of carbon monoxide and air at least once every 31
days. When the carbon monoxide concentration at this location reaches 50
parts per million, the heater causing the elevated carbon monoxide level
shall be shut down.