Any vessel storing carbon compounds composed only of carbon, hydrogen, or oxygen is permitted by rule, provided that the vessel vent is directed to an incinerator, boiler, or other firebox having a stationary flue or a waste gas flare system that will operate with no visible emissions except as provided by Chapter 101 of this title (relating to General Air Quality Rules) for periods of maintenance or operational upset. However, vessels not exceeding 100 barrels capacity and storing only liquid petroleum gas may have the safety relief valve vent directly to the atmosphere. Also, any tank having a capacity not to exceed 1,000 gallons and storing only commercial odorants used to odorize petroleum gases may have the safety relief valve vent directly to the atmosphere.