49 CFR § 232.107 - Air source requirements and cold weather operations.
(a) Monitoring plans for yard air sources.
(1) A railroad shall adopt and comply with a written plan to monitor all yard air sources, other than locomotives, to determine that they operate as intended and do not introduce contaminants into the brake system of freight equipment.
(2) This plan shall require the railroad to:
(i) Inspect each yard air source at least two times per calendar year, no less than five months apart, to determine it operates as intended and does not introduce contaminants into the brake system of the equipment it services.
(ii) Identify yard air sources found not to be operating as intended or found introducing contaminants into the brake system of the equipment it services.
(3) A railroad shall maintain records of the information and actions required by paragraph (a)(2). These records shall be maintained for a period of at least one year from the date of creation and may be maintained either electronically or in writing.
(d) Yard air reservoirs shall either be equipped with an operable automatic drain system or be manually drained at least once each day that the devices are used or more often if moisture is detected in the system.
(e) A railroad shall adopt and comply with detailed written operating procedures tailored to the equipment and territory of that railroad to cover safe train operations during cold weather. For purposes of this provision, “cold weather” means when the ambient temperature drops below 10 degrees Fahrenheit (F) (minus 12.2 degrees Celsius).