The smell of Natual Gas coming through my ventilation

GMC Sierra C3 6.0 liter. This smell started in the beginning of December 2010. I smell it when the heater is running and the fresh air vent is open. When I run the recirculation the smell goes away, or at least does not get stronger. I just changed the cabin air filter to no effect, and have used a mold treatment in the ventilation tat had done little for the situation. Has anyone else had this issue, or have an answer to this conundrum?

natural gas as in what powers your furnace?

I’d suspect a dead rodent (or a gas leak in your garage but I think you’d be able to detect that outside of your car). Sometimes mice crawl in the air vents and then die. The corpse can smell kind of like natural gas.

I am going to have the vehicle looked at tomorrow by my mechanic. I thought it might be something to that effect, but I thought it would smell worse.


The catalytic converter has a similar smell. Could be an exhaust leak. Have it checked ASAP.

I thought the CC has the smell of rotten eggs, hydrogen sulfide, when it goes. The exhaust leak is a possibility. Hopefully I will know more tomorrow.

They add an odorant to natural gas that smells something like rotten eggs. Is this what you smell? If it is, it could be sulfur gas being released from the battery from a low cell in the battery. If possible check the electolyte level in the battery cells and add distilled water to any cells that have a low level. If it’s a no-maintenance battery where the cells can’t be checked for electrolyte levels, the battery may require replacement.


Nat. gas has mercaptan added to it which gives it a rotten egg smell…similar to cat. convert. smell.

The battery does need to be replaced soon. I had no idea that that could be the issue, but it make the most logical sense. I should get that replaced before I do anything else.

It is not sulfur that I smell but Natural Gas.

If the engine doesn’t operate on CNG, then the only source for the smell is from the exhaust or the battery.


It was the battery, to weird