Bad smell in house could be a plumbing vent issue

My vent for the kitchen drain has seen better days! 

 
If a bad smell in my house is NOT one of my three sons then it is most likely a plumbing issue. We recently had a bad smell emanating from under our basement staircase. We followed the kitchen drain down to the vent stack tie-in located in the wall  adjacent to the stairs. After some demolition and investigation we discovered corrosion and cracks in the original cast iron vent pipe. Old Chicago bungalows will have cast iron vents and waste stacks when plumbing is original.

A sewer smell (or reoccurring general bad smell) in the home can be caused by a corroded drain vent pipe (like shown above) or a damaged bathroom waste stack. The problem is these vents are in the wall so it often takes some drywall demo to locate the issue. Check for any water leaks, mold or possible rodents (oy). If things all check out but there is still a consistent bad smell it could very well be a vent or waste stack issue.