Abstract: A gasketed hatch cover usable in an odor control system in a wastewater treatment plant or in other installations provided with a hatch opening which when closed by the cover is then sealed to prevent the escape of fumes into the atmosphere. The hatch opening is bordered by parallel side walls each having a ledge projecting therefrom. The cover is formed by a rectangular plate whose long edges are turned down to form rims that rest on the ledges and are spaced from the side walls of the opening when the cover is closed. Fitting on each rim is a replaceable gasket of compressible material having a J-shaped section defining a channel to snugly accommodate the rim between the parallel short and long legs of the J, and a D-shaped section whose straight leg is common with the long leg of the J-section. When the gasketed cover is closed, the D-shaped section of each gasket is then compressed within the space between the rim and the side wall, thereby sealing the opening.