The utility model relates to a ventilation blower casing, wherein this ventilation blower casing has the outer casing that is used for holding the case main body of ventilation mechanism spare and surrounds this case main body along the circumference direction, wherein case main body has two at least lath and/or this outer casings that extend in the circumference direction in its radial outside and has two at least ribs that extend in the circumference direction in its radial inboard, lath and/or rib have formed between case main body and outer casing and have been used for holding and keeping the heat band under the confined state, the passageway that surrounds in the circumference orientation, and wherein the outer casing has at least one guiding rib, the guiding rib is and extend in the circumference direction in directional case main body of radial direction and passageway. From this can be enough also can to be this casing in order installing additional and to be equipped with the heat band in its outside in initial assembly, and need not for this reason and get rid of whole outer casing. In addition, should realize using the outer casing of different shapes, for example hexagon or octagonal shape in overlooking the angle.