If your home has natural ventilation it is reliant on the natural elements to function. In the majority of cases the chimney is used for the outlet while window vents, doors and general vents around the house are used as inlets. Wind conditions can cause a back draft through you home causing damp air or ash to be forced into your home through the chimney
Installation of a Supavent on your home is inexpensive and will alleviate any such problems. The operation of the vent creates a vacuum in your chimney and therefore causes the air to be drawn out. Back drafts will never be a problem as the stronger the wind the more suction created.