Over the past few years and always this time of the year (fall) we have noticed a sewer smell in a walk-in closet area of the house. It always seems to occur when the days are warm but the nights and mornings cool down significantly (We live in Ohio). Once the day starts to warm up again the smell disappears. Then when the daytime temperatures do not rise so high (late fall or winter), it's gone until the next year. We have had plumbers do smoke tests, inspect vent systems (from the attic, what they could see anyway) and snake sewer lines with no findings. The most confusing and frustrating part of this is the walk-in closet area where the smell originates has no plumbing fixtures whatsoever and sits over a concrete slab. We have spent thousands of dollars without any relief and we are at our wits end over this. Has anybody ever experienced anything like this or have any suggestions? It would be greatly appreciated!