What's that smell?!

So within the last hour and a half or so my trailer smells like eggs and farts. Sorry I don't know how else to explain the smell. At first I thought it was my dog but further investigation shows its coming from under the cabinets. Not the sink cabinet either the one by the door under the stove. Their is a black pipe there that goes from the sink then splits up the wall and underneath the trailer. It even smells in the bread box cabinet. And when you bend down by the door right above the floor its horrible. I've smelled the underbelly and its not there. Not around my fridge or bedroom/bathroom. I've aired it out and it goes away but as soon as I close the door again its back. The only thing I've done today that I don't do everyday is drain the black tank. But it never smells like this when I empty it. I always close my Grey tanks when I empty it also. I think that black pipe is the culprit but I don't know what it is exactly.