Chimney Caps, chimney rain caps, chimney spark arresters, chimney tops, you may even call them by another name but what do they do anyway? Some folks believe that a chimney cap will kill your draft. Other folks believe that they are for asthetic purposes. Some people have no idea what they are or why they would need one. 
For those of us who have heard some scratching noises in the chimney or have had a certified chimney sweep come out to remove a decaying, rather pungent smelling animal, the concept of having a chimney cap installed can be fairly straight forward and easy to understand. What if that's not the case? Should you still consider having a certified chimney sweep install a chimney cap for you?
Rain, sleet, sno
w and ice are fairly common in New England. Lately, the heat has been beating down on our chimneys too. Even though it's not overnight, these extreme temperature and humidity fluctuations have their toll on any masonry. A full size and properly installed chimney cap will protect the inside of your chimney flue, and will keep out animals who will compete to nest in your chimney.
Chimney caps protect your chimney, the appliances that vent through your 
chimney such as fireplaces, woodstoves, oil and gas fired burners and other types of equipment. They also protect the animals in your neighborhood from getting stuck in your chimney or roasted alive when the flue is in use. When you combine all of the potential hazards that commonly become present with the cost associated with fixing the problems that are commonly created by these hazards, having a professional Chimney Sweep install a cap for you will be relatively short money.
Chimney caps p
rotect the local wildlife. I don't know how many carcasses our technician's have scraped off of dampers, pulled out of gas flues, or live animals they've chased out of clean out doors and vent pipes but I'm certain that it's too many. Truth is thousands of animals die each year because they nest in chimney flues and it can be prevented simply. To stop these kinds of things from happening, have your certified chimney sweep install a stainless steel or copper chimney cap, make sure they are seeing/inspecting all parts of your chimney with a camera to ensure there are no breeches or flaws in the flashing and other critical components of a healthy chimney, and please, have your chimney inspected and swept yearly.