Location
Where there is no superheater, the snifting valves are mounted directly on the cylinders or steam chests. The drawback of this arrangement is that they admit cold air which cools the cylinders and leads to condensation when the steam is turned on again.
If a superheater is fitted, one or two snifting valves may be mounted on the "wet" side of the superheater header. This causes air to be drawn through the superheater and heated so that it keeps the cylinders warm. Different railways had different ideas about the merits of drawing air through the superheater elements when coasting.
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