Vented gas cap-- ok in garage that is under the house?

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MRGTX

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I live in a ranch style house which means that part of my basement also serves as the garage. This is fantastic in the sense that the garage is basically heated...but there are some obvious worries here too.

So I believe that in almost any case, there will be some fuel vapors escaping from a car with gasoline in it...but I'm wondering if a vented cap (in lieu of the carbon canister) might present more danger.

When doing the motor swap in my car, the canister came out and I plugged off the line. Now, I'm in a situation where out of habit I pop open the gas cap every time I stop driving to relieve the pressure...not ideal of course but at least the fumes are contained when the car is parked since it's essentially "in the house." Before I order up the new cap, is correct that a temperature change in the garage cause a build-up of pressure and subsequently, a release of fuel vapors...into the garage?

...Or am I overestimating the danger here?

Thoughts are very welcome.
 
a vented cap will vent the gas fumes to the atmosphere (read, your garage/home)
a properly working canister will not "vent" at all
it will store the fumes in the canister untill you fire up the engine
then a valve operated valve will open and the fumes stored in the canister will get released into the PCV system, sucked into the engine and burned of

if it were my car, my home and my family, i would go through the trouble of reinstalling a canister
as a matter of fact, when it came to my car, that is exactly what i did

(this thread has partnumbers and pictures of my setup)

Vapor/Charcoal Cannister
 
Thanks for confirming...I often stay up nights thinking about gasoline in the house. The vented cap seems like it will only make the situation worse.

Yep...I will look into a new canister. The old one had failed with the carbon media blasting out of the bottom some years back.
 
I would park a car in there under precisely zero circumstances, if you have a gas water heater.
 
Before the 1970's emission controls, people parked cars with vented gas tanks in all kinds of garages. Some of which were surely under their houses. I don't recall ever hearing of gasoline fume explosions or any other problems caused by these vent-to-atmosphere fuel systems. Why do you think this will be a "problem" in 2017, when it was not a problem in 1967?
 
Before the 1970's emission controls, people parked cars with vented gas tanks in all kinds of garages. Some of which were surely under their houses. I don't recall ever hearing of gasoline fume explosions or any other problems caused by these vent-to-atmosphere fuel systems. Why do you think this will be a "problem" in 2017, when it was not a problem in 1967?
if you are still worried, install a vent for the garage. You can put it on a timer, and cycle it once or twice daily.
 
i reinstalled the canister on my car and aside from the smell being better I also noticed a HUGE difference in how much fuel was disappearing from the tank if the car sat for a few days undriven. It was substantial, now the car has the same amount of gas in the tank as it did when I shut it off. :)
 
Before the 1970's emission controls, people parked cars with vented gas tanks in all kinds of garages. Some of which were surely under their houses. I don't recall ever hearing of gasoline fume explosions or any other problems caused by these vent-to-atmosphere fuel systems. Why do you think this will be a "problem" in 2017, when it was not a problem in 1967?

if you are still worried, install a vent for the garage. You can put it on a timer, and cycle it once or twice daily.

Exactly.

The lower explosive limit for gasoline is 1.4%. That would mean that the air in your garage would have to be 1.4% gasoline fumes before you could have a widespread explosion. Simply put, the odds of that happening are about nil. Your garage would have to be perfectly sealed (it's not), and it would have to be hotter than hades in there to vaporize that much fuel out of your gas tank vent all at once. The fumes coming off the gasoline in your tank under normal conditions would have an incredibly difficult path to reach the LEL. I'm not saying it's 100% impossible, but, it would have to be a pretty extraordinary set of circumstances. Now, if you had a drain catch pan full of gas sitting next to your water heater that's a different situation, that could flash off pretty easily. But that would be a localized flash, it still wouldn't be a widespread explosion. And we're talking about the fuel in your tank coming out of a small cap vent, not a pan with a large surface area of fuel exposed directly to the atmosphere near a heat source.

Now, that doesn't necessarily mean that you want the fumes coming off your car hanging out in your garage for other reasons. Like the fact that they're carcinogenic, which they didn't care about in 1967. The way around that is to have a vented garage, which, btw, you probably have already because in most places its required by building code. Even more true if you already have natural gas appliances in your garage (water heater, dryer, etc.), and doubly true because your garage is attached and below your living space. Although the relevant building code depends on how old your house is and where you live too.

Not that the charcoal canister is a bad thing, it's really not. Like a PCV valve, they're actually a pretty handy thing that came out of smog controls. Adding that back into your fuel system would be a pretty easy way to eliminate any real possibility of fumes. But more than likely the biggest issue with the vented cap in your garage will be the annoyance of smelling some gasoline in close proximity to your car on really hot days. For that matter, where do you think the fuel in your carburetor fuel bowls goes? Even with a "closed" fuel system your still have fuel exposed to atmosphere if you've got a carb. And any owner of an edelbrock or carter carb can tell you those fuel bowls are dry after a few days of sitting in a hot climate. Mine always were. 3 days or more without a start up on my Challenger and you had to crank until the fuel bowls refilled before it would start, and that car has a charcoal canister.
 
I would park a car in there under precisely zero circumstances, if you have a gas water heater.

Yep. A very good call. I have an electric heater which makes me feel only a little better.

Before the 1970's emission controls, people parked cars with vented gas tanks in all kinds of garages. Some of which were surely under their houses. I don't recall ever hearing of gasoline fume explosions or any other problems caused by these vent-to-atmosphere fuel systems. Why do you think this will be a "problem" in 2017, when it was not a problem in 1967?

You're completely right about that...it sure seems like a terrible idea but somehow, it seems to have worked out.

People also used to breathe in leaded exhaust fumes all day long too. :D
 
The electric heater, refrigerator, and gas appliance "problem" (if there is one) is normally solved by following building codes, which in most places say that any igniter, spark (motor), or pilot light in a garage must be at least 12" off the floor (many places say 18"). This is because almost all fumes (gas, gasoline, paint, etc...) are heavier than air and will always settle at the floor level.
 
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