4. Chimneys
Chimneys make a cozy atmosphere during the winter, but they can be hazardous if not cleaned routinely. Soot can build up inside the chimney, making smoke harder and harder to exit. This can put you at risk for everything from carbon monoxide to house fires. 

An easy way to maintain your chimney is to burn Creosote Sweeping Logs to break down the tar stuck inside. You should also clean out your chimney each year before fire burning season. The Spruce has a great step-by-step guide on how to do it yourself here.