Every chimney in California is required by law to have a well secured properly sized spark arrestor. The spark arrestor is mounted to the top of the chimney and has many functions. It's primary and legal function is that it limits the amount of embers or "sparks" that escape the chimney. The spark arrestor also blocks and birds, animals etc from getting inside the chimney. These things can cause blockages which in turn causes a backup in smoke and is a huge fire risk. Th main benefit of a spark arrestor in my opinion is its ability to block rain from getting inside the chimney. Water or moisture is the worst thing for a fireplace. Moisture caused cracks which in turn allow chimney fires to become house fires. So even if you don't use your fireplace a spark arrestor is necessary. The spark arrestors that we sell are all stainless steal and cost $179 installed.