ABS provides a VEC notation for owners wishing to control vapour emissions. VECs enable a vessel to return vapour displaced during loading operations back to tanks ashore instead of releasing the gases into the atmosphere. The ABS VEC notation will provide compliance with the VEC standard recommended by MARPOL Annex VI subject to the Administration's acceptance of automatic shut-down valves, if fitted. Whilst VEC is not yet mandated, there are provisions for vapour emission control requirements under MARPOL Annex VI enabling signatory Countries to institute VEC requirements for ports and terminals under their control. IMO must be notified at least six months in advance of such an intention. Where terminals or ports have VECS, non-VECS tankers can be accepted by signatory Countries for up to three years after notification to IMO.

It should be noted that US based legislation on vapour emission control systems varies between states. Controlling flammable and combustible organic vapors presents numerous hazards including cargo tank overfill, overpressure or vacuum, cargo spillage, and fire and detonation of the flammable vapors. Under the authority of section 183(f) of the Clean Air Act, the Coast Guard has issued regulations to ensure the safety of equipment and operations of VCSs that control vapors of crude oil, gasoline blends, or benzene emitted from a tank vessel's cargo tanks.

These regulations are treated separately in the Code of Federal Regulations for vessel and facility requirements. In general, the Subchapter D, tank vessel regulations in 46 CFR part 39 contain requirements for vapor collection equipment installed on tank vessels, while the regulations in 33 CFR 154 Subpart E, contain the requirements for facility based vapor control systems.Important areas addressed by these regulations include:

• Cargo gauging system (§39.20-3);
• Tankship liquid overfill protection (§39.20-7);
• Vapor overpressure and vacuum protection (§39.20-11);
• High and low vapor pressure protection for tankships (§39.20-13);
• Operational requirements (§39.30-1);
• Lightering and topping-off operations with vapor balancing (§39.40);
• Personnel training (§39.10-11).