Abstract: An improved petroleum vapor control apparatus for scrubbing petroleum vapors at high flow rates without generating dangerous levels of backpressure. The apparatus comprises a substantially air-tight housing into which petroleum vapors are ducted. The vapors are passed through an activated carbon adsorber bed having a large-diameter outlet, after which the scrubbed vapors pass into a zone of controlled pressure. The scrubbed vapors are then vented to the atmosphere. The housing is preferably able to withstand marine conditions, so that the apparatus can be used on marine barges which carry petroleum products.