Mine Safety and Health Administration 30 - Outdoor Storage Locker

56.4531 Flammable or Combustible Liquid Storage Buildings or Rooms

(a) Storage buildings or storage rooms in which flammable or combustible liquids, including grease, are stored and that are within 100 feet of any person’s work station shall be ventilated with a sufficient volume of air to prevent the accumulation of flammable vapors.
(b) In addition, the buildings or rooms shall be—
(1) Constructed to meet a fire resistance rating of at least one hour; or
(2) Equipped with an automatic fire suppression system; or
(3) Equipped with an early warning fire detection device that will alert any person who could be endangered by a fire, provided that no person’s work station is in the building.
(c) Flammable or combustible liquids in use for day-to-day maintenance and operational activities are not considered in storage under this standard.

Please consult your local authority having jurisdiction with your questions and for guidance in conforming to laws as they apply to your application. This is only meant for a reference and does not imply a warranty.