There is nothing that can cause a gas smell from your heater. There are however a few possible reasons why you experience a gas smell. One could be that fumes from the exhaust are entering the passenger compartment.The other possibility is that your heater could be leaking and what you are smelling is coolant or antifreeze as some people call it. The heater consists of a small radiator and a fan, it circulates hot water from the cooling system through the radiator and the fan blows air through the radiator just like the radiator in front of your car. There is nothing that can cause a gas smell during this process. Check to see if your exhaust system does no have a leak by holding a rag over the tailpipe and get someone to listen at the front. The chances are that the fan is drawing in exhaust gas and circulating themn in the passenger area.
behind the glove compartment inside the heater assy
Check inside the car undre the dash , check the heater core.
A bad exhaust will cause gas fumes to get inside the Nissan Maxima while it is idling. Gas fumes, if contained in an enclosed space, is dangerous.
The heater core is under the passenger side of the dashboard inside of the housing that holds and covers most of the A/C an Heating system components. IT is NOT easy to change.
Your heater core is leaking you probably also noticed the heater may not be working as well.
if you smell it inside, it's the heater core it has a leak.
the heater fan resister,it is or should be on inside or on outside heater box.
Is inside the distributor
Either the heater core is leaking, the windshield is leaking, or there is a leak around the cowl. If the water tastes sweet it is a leaking heater core.
it is inside the distributor
the heater core, heater core hoses or heater control valve is leaking
If it is leaking inside the car, the heater core has failed.If it is leaking inside the car, the heater core has failed.