Why do I smell exhaust when my hot water tank has been idle for a day or two?
Answers:
Fumes from the pilot light burning.
When the unit is heating water, the heat from the burner is sufficient to propel exhausts up the flue, but when it sits idle, the heat from the pilot does not. Also, ambient winds can blow drafts though the flue.
You may also have a problem with an obstruction in your flue, or a poorly set-up flue system.
Other answers:
can your local gas company asap
can your local gas company asap
You had better have a professional look at that......NOW!
Check to see if its venting properly. When its running use something that produces smoke like a match, etc to ensure it is being drawn into the draft hood. Be sure its not blowing out the back or sides. If its venting properly then the baffle may be getting clogged which would cause the pilot fumes to back up and spill out the burner chamber when not in use. That said be sure that you are smelling exhaust fumes and not a gas odor. Sometimes they can be hard to tell apart.
If its not a gas odor and it is venting while in operation then you may have a problem with air being drawn into The home by th Central air unit or an exhaust fan, which is a dangerous problem on its own. If its in a closet it should have vents installed for fresh air and venting, either 1 large one or 2 smaller ones. Be sure they are clear and working.
Sounds like a bad vent. Maybe not enough slope in the vent pipe, or disconnected somewhere.
My guess is that making it run throws off enough heat to get a draft going, but the heat from just the pilot is not enough to get it going and the fumes are escaping into the house.
apparently you have a gas hot water heater. You are smelling the pilot if it is idle.
Your chimney or flue may be plugged or have leaks.
If this is a relatively new situation have a repairman check it out.
If it has always been like this and the room is small it is probably normal pilot smell.
That doesn't sound right! You might want to get it looked at and make sure there isn't a leak or a blockage somewhere.
Good luck!