We’ve lived in our 1940s home for 4 years, but over the last 1 year we have begun to smell a rotten cabbage/vegetable smell (rather earthy) in the kitchen and sometimes in the adjacent boiler room. It comes and goes. It seems worst in the winter when it is cold and especially when it rains.

The smell seems most strong under the kitchen sink in the cupboard and under the dishwasher, which is right next to the sink. Sometimes we smell it outside the house right about the spot we smell it inside. The smell is close to the floor but wafts upward. Our boiler flue is nowhere near this area and we already checked for any clogging.

We’ve cleaned the dishwasher and disposal, pulled out the P trap to check for build-up, checked for evidence of leaks, checked for mold, nothing.

A few more points: the underside of the dishwasher seems to smell particularly strong (not inside the unit but underneath if you pull it away from the wall). And we also discovered a hole behind the dishwasher that someone else had cut out, and we did smell the smell wafting up from that hole.

Any advice is appreciated.