Chimneys use a lot of air to fuel their fires. This air has to come from somewhere. Some houses are so air tight that a negative-pressure system can develop, ensuring that your fire will not draft properly. This problem can be made worse by other appliances competing for the same air (i.e. Range hoods, bathroom vents, clothes dryers, forced draft services.
Fortunately this problem is very easy to diagnose. If your chimney is beginning to smoke you can crack a nearby window or door and the draft should fix itself. Mike’s mobile can install an air vent for makeup air if this is your problem. These vents can be closed when not in use so energy is not wasted.