heya guys while driving my deli yesterday i started to smell a bad sort of gassy(wasnt me i swear

) coming from some where after about 10 mins of this i was getting a head ache so down went the windows. I dont think i was the diesel smell since i took a good whiff from the gas tank. I lifted the motor cover and no smell was from there either. So the only thing i can think of was the AC coolant since i put some of my lunch in the cool box earlier in the week and maybe the smell came from there since i dont really know the smell of AC coolant.
Any1 have a clue on what this could b?