Glove should not inflate - gently draw glove into engine. This is how the fumes are drawn out and into the engine via a valve, they should be sucked out hence the slightly negative pressure.
Some PCV valves have diaphragms inside that can split - unsure if the Volvo ones do. Also the pipework may block.
There is a good explanation here.
https://www.youtube.com/watch?v=EPIfI9aZHt4