My fireplace pulls smoke into my home.

When the conditions are right, and if you have a chimney with multiple flues in it, the flue that serves the lowest level can sometimes pull smoke back into the home.  Once we understand how our chimneys function we can explore some possible explanations for  why this may be occurring. 

The air inside your home is at a higher pressure relative to the air outside your home.  Think of a balloon that is full of air.  When you blow it up and pinch it off at the mouth piece, the balloon holds air at pressure.  If you release the mouth piece the air is rapidly propelled out because it is under greater pressure while inside the balloon.

When we heat air in our home (from a heater or from sunlight) the hot air rises to the higher levels and builds pressure in the structure.  Our homes are not completely air tight and this high pressure air leaks out of the upper levels.

 When you view your home as a complete system think of a hot air balloon then it becomes clearer what is happening.  When air leaks out of the upper level new air must be introduced at the lower level.  If you have a fireplace or flue in the lowest level of the home that is the easiest place for this make up air to come in and replenish the lost air.

Let us explore possible solutions to this phenomena.  Your first assignment is to seek out potential air leaks.  Examples of things you can do to minimize leaks would be to caulk your windows and doors and inspect their weather stripping.  You also want to make sure you have adequate insulation in your attic as well as a proper seal for your attic access door.   

If this condition just recently started you must consider any changes that have occurred that may have brought this effect on.  Some things to consider would be a home addition or project that was not properly sealed.  A new skylight or changes made to a dryer vent on an upper level.

If  you cannot figure it out then it is time to call in the experts.  There is a procedure called a blower door test administered by efficiency companies and this test can help figure out from where your home is depressurizing.

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