I have just got Honda Fit 2009. We had compressor changed a few months ago so the air con works better. Changed the internal air filter.

When we drive the car smells of gas / chemicals.

If we have the a/c on it smells worse, and if we set the air to recirculate it smells terrible in the cabin!! so much so you can taste the fumes!! If you have it on 'normal' intake it is not bad in the car but it still smells if you stand near the car.

We have checked the spark plugs but I will get a mechanic to check again.

Is anything obvious to you guys?

car has done 80 000KM

 

The air intake for the cabin is essentially located in the engine bay. It's below the wipers in front of the upper glove box.

I would start by checking that all the spark plugs are tight. A second culprit could be an exhaust leak.

FYI, I would deal with this sooner rather than later - breathing in various chemicals from combustion process or exhaust is not good for you in a general sense but could also be acutely dangerous (e.g., carbon monoxide toxicity). If you have to drive the car at the moment I would recommend lowering the windows to get as much fresh air as possible.