An apparatus and method for forming an opening through a storage tank (3) containing a flammable and/or combustible fluid, for example petrol. The storage tank (3) includes a hollow column (7) extending outwardly from an exterior surface of the storage tank (3), an interior wall of the hollow column (7) in combination with the exterior surface of the storage tank (3) defining a well-like cavity allowing access by the apparatus (1) to the exterior surface of the storage tank (3). The apparatus (1) includes a cutting assembly (13) for cutting through the exterior surface of the storage tank (3); and a housing assembly for supporting the cutting assembly (13). The housing assembly includes a sealing assembly for sealing the housing assembly with respect to the hollow column (7) such that the cavity is sealed from surrounding air. The housing assembly further includes a fluid circulation assembly for passing nitrogen into the cavity such that a non-flammable environment is provided within the cavity during cutting of the opening. The opening is thereby safely cut without generating ignition sources such as sparks and flames. Flammable vapor is also prevented from escaping into the surrounding air. In addition, the storage tank (3) does not need to be emptied of fluid prior to the commencement of the cutting process.