That's a good point but usually it still runs but very poorly, Stihl (pun) worth pulling it and checking. Takes a 15mm deep socket to remove it at the muffler outlet to check and worth as noted to check now and on a regular basis. You can use a propane or mapp gas torch to clean (burn) it and you can watch the sparks fly too as you're burning it clean and see how it did its job containing those sparks