30 CFR § 77.306
Fire protection.
Based on the need for fire protection measures in connection with the
particular design of the thermal dryer, an authorized representative of the
Secretary may require any of the following measures to be employed:
(a) Water sprays automatically actuated by rises in temperature to
prevent fire, installed inside the thermal dryer systems, and such sprays
shall be designed to provide for manual operation in the event of power
failure.
(b) Fog nozzles, or other no less effective means, installed inside
the thermal dryer systems to provide additional moisture or an artificial
drying load within the drying system when the system is being started or
shutdown.
(c) The water system of each thermal dryer shall be interconnected to
a supply of compressed air which permits constant or frequent purging of all
water sprays and fog nozzles or other no less effective means of purging
shall be provided.