Abstract: A manhole sealing device enables the recovery of vapors displaced from a tank during the process of filling a tank with fuel, through the manhole. The sealing device comprises a sealing gasket, which has an inflation chamber defined by two tubular walls. When the chamber is inflated, the gasket is distended to toroidal configuration capable of sealing engaging manhole inner diameters of a wide dimensional range. The sealing gasket is mounted on a lock-down bar what is clamped against the upper end of the manhole, using bolts that are also used in clamping the hatch cover for the manhole. Preferable the gasket is first inflated to centralize it relative to the manhole and then clamped in fixed relation relative thereto.