Ok...I came home last night and my house smelled FOUL.  We searched the house for a forgotten sandwich, or dirty diaper that didn't make it to the bin...and we've found nothing.  I checked my neighbors and no one has died or is missing in the building so that's out.  I think something crawled into my vent and died.  I can smell it particularly in one Main vent line so I'm pretty sure I know where the offending corpse is.  It's just that the line is embedded in drywall and I can't get to it through the basement.  I've peeked in all the vent lines with a flashlight and a mirror and can't see anything.  Does anyone have any suggestions? 

PRH