The ACOP to the regulations says that enclosed workplaces should be sufficiently well ventilated so stale air, and air which is hot or humid because of the processes or equipment in the workplace, is replaced at a reasonable rate. Air which is taken from the outside can normally be considered to be “fresh”, although air inlets should not be sited, for example, close to a flue, an exhaust ventilation system outlet, or an area in which vehicles manoeuvre.