Yes the oil trap basically takes the place of a PCV valve. These are common replacements on Volvos as well as many other make of cars. Usually these tend to get plugged up after about 60K miles or more. More likely to have issues if the car is driven for very short runs without allowing to get fully warmed up. This causes sludging up of the trap. Overfilling the crankcase oil can also create issues with the oil traps. If the oil trap plugs it will cause a squealing sound and also build up excessive crankcase pressure that can cause oil leaks and seal or gasket failures. A properly operating oil trap will cause a slightly negative pressure in the crankcase which will prevent oil leaks or seal leaks. If you drive short distances mostly I would advise changing the oil more regularly than the Volvo recommended service intervals to prevent this from happening.