To expand the application of the National Building Code of Canada to existing buildings in regard to access from the exterior of the building into rooms used for the storage of cylinders of Class 2.3 toxic or corrosive gases, or Class 2.2 (5.1) oxidizing gases and closures leading to the interior of the building from rooms used for the storage of cylinders of Class 2.3 toxic or corrosive gases, or Class 2.2 (5.1) oxidizing gases.