I've recently been smelling a strange odor from my office area these past few days, and I checked my vents and discovered this (in the photos). It is a purple, bar of soap-like substance with bubbles/air pockets on top. It kind of reminds me of a moisture absorber. There's a white ring where it touches the floor, which makes me think of soap, but I have no clue what this may be. There is also a yellow, goo like substance on the floor of the vent- to which I have no clue what it truly is. I haven't been able to investigate it further because it is very late, and I do not wish to poke nor prod at it. I apologize for the photo quality, my camera is not the best and I did not want to drop it into the vent. This house is old, so maybe it was something the previous owners put in here. But I JUST started smelling it. It is not overbearing whatsoever, and it's slightly unpleasant. It almost smells like flour.