When a gas oven doesn't smell delicious, it may be because you didn't get the recipe right, but there are other sources of strong odors even more serious than that. A rotten egg smell is a red flag. It means there's a gas leak, so turn off the gas until you get to the bottom of it. New ovens have an unpleasant odor that goes away after several uses, and some smells just mean the oven needs cleaning.
Rotten Egg Odor
Propane and natural gas are both available for residential use; propane, a petroleum byproduct, burns hotter than natural gas, which occurs naturally in the earth's crust. Both gases are naturally odorless, so suppliers add methyl mercaptan to natural gas and ethyl mercaptan to propane to give them the distinctive rotten egg smell. This odor is a safety precaution -- whenever you smell it, you know there is flammable gas in the air and that you should not, under any circumstances, light a flame. Even turning on electrical appliances is dangerous, because they produce sparks.
If you smell rotten egg odors coming from your gas stove, check the controls -- someone may have forgotten to turn off a burner or the broiler. Turn it off immediately. If someone left the broiler on, open the oven, and open the windows and doors and get everyone to go outside until the smell dissipates. If no controls were left on, and you can't pinpoint the source of the smell, find the gas valve and turn it off. You may have to slide the oven out to access the valve. The source of the leak may be a loose connection -- and it may be easy to fix -- but first you need to let the gas dissipate. Open the windows and go outside.
Finding and Fixing a Leak
It's safe to go back in the house when you can no longer detect the rotten egg odor, and at this point, it's safe to look for the leak.
Open the gas valve. You may hear hissing coming from the valve or the stove, which makes finding the leak easier.
Mix a 50-50 solution of dish soap and water, and put some in a spray bottle. Spray the gas valve, the connections to the stove and the gas line in between, and look for bubbles.
Tighten the connections if you see bubbles forming around the connection at the gas valve or the stove. You need to replace the gas line if you see leaks coming from any point along its length.
Turn the gas off and call a service technician if you can't pinpoint the leak. It's probably coming from some place inside the stove -- perhaps the gas control valve -- and it's dangerous to try to service that yourself. Leave the gas off until the leak has been repaired.
New Oven Smell
If your oven is new, expect it to have a distinctive odor. As long as it isn't mixed with rotten egg smells, it's completely safe -- although it may be unpleasant. It's produced as the insulation around the oven compartment off-gasses. If you have a self-cleaning oven, you can make this smell go away more quickly by running the self-cleaning cycle at least once.
The self-cleaning cycle produces high temperatures -- more than twice what's needed for cooking -- which vaporize fats and grime that collect on the inside of the oven. It's normal for the oven to emit smoke and odors during the self-cleaning cycle -- you should operate the exhaust fan to blow them out of the kitchen. The fact that these odors are inevitable and not entirely harmless may be a reason to limit your use of the self-cleaning feature.