Ken and Jot have this correct. I always have the flame trap serviced on my non-turbos (The turbo doesn't have one) and I've cleaned it myself a few times. When getting it serviced, some mechanics clean the little nylon screen, which really cannot "wear out". I just had my son's non-turbo serviced this week....bill says "Flame Trap Kit", $12.75. Having had this screen out myself, I have no idea what the "kit" is. The crankcase ventilation works fine without this little trap, and the risk of a backfire in a volvo seems minute. I've considered leaving the screen out. It seems that if you are not going to check it every 10,000 miles and clean it, the next best option is to take it out to avoid pressure build up.