Chevrolet Repair: Fuel system, chev cav, fuel injectors

Question
First forgive me, I don't know alot about cars. I have a 92 Chev Cav 4 cyl and when I am just sitting idling it seems like my fuel system is leaking out through the heater.  I had my brother come check it out one day and it was one of the fuel injectors leaking gas.  We did the O-ring thing and everything was working fine for a few weeks and then it started again.  I once again stopped driving the car and I took it to a local mechanic as soon as I could.  Which turned out to be a couple weeks later.  There was no smell and no leak.  Once again 2 weeks later and it's back again.  Do I need a new fuel injector or any of these other things that I have been trying to understand since researching this problem.  Any information or advice you could give me would be wonderful.  

Answer
Hi Jayleen,
By leaking through the heater, I assume you mean you smell gasoline.
If there is gas leaking on the engine, it should be found and fixed before it starts a fire.
Obviously, if it isn't leaking at the mechanics, he can't fix it.
Ask him if you can bring it in as soon as you smell gas, and then do it.
It is possible that the vapor canister was filled, especially if you had just filled up with gas.
See if you can smell it right after filling up.
Van