Propane released when lighting burner

[NotreVoyage]

What happens to propane released when lighting a cooker burner. It takes a few seconds to light the burner and in that time a little propane is released. It is heavier than air so I guess it ends up in the bilge. Overtime will it accumulate, disperse naturally or decay?

It is only a small amount but over time does it accumulate?

Anyone know?

Thanks

[zeehag]

i have not yet died nor exploded
knock wood.
i find no trace of it post ignition, which seems to use all the escaped gas.
have fun.

[Boatguy30]

I would assume it evaporates after some time as gasoline does.

[BlackHeron]

Good question. LP, "Liquid Propane," evaporates into a gas at the top of the bottle and is drawn off into the hose and through the regulator. It is already "evaporated" after this point. A gas can't evaporate again unless it is first condensed into a liquid again.

Propane gas is heavier than air. It sinks. It can't evaporate, it simply drops down to the lowest place it can settle into. From there, can it slowly mix with the air and atom by atom bounce up and out of the boat eventually?

Like Karen said, I haven't blowed up already.

We have a Fireboy-Xinex LP sensor in our dry bilge as part of the solenoid panel. It goes through a self-test every time it starts up and thereafter monitors the air in the bilge for traces of propane and other dangerous gases. But it isn't quite down at the very bottom of the wet bilge. It wouldn't survive the moisture. Every once in a while I will take my portable gas sniffer and put it down there and check when I'm sniffing around the stove for leaks. It never has shown any trace of explosive gases.

Where does it go? It must migrate out slowly somehow.

[Jammer]

Originally Posted by NotreVoyage

What happens to propane released when lighting a cooker burner. It takes a few seconds to light the burner and in that time a little propane is released. It is heavier than air so I guess it ends up in the bilge. Overtime will it accumulate, disperse naturally or decay?

It is only a small amount but over time does it accumulate?

Over time propane dissolves in air forming a solution. Between 2.1% and 9.5% propane this solution is explosive. Propane, and solutions of air and propane, are heavier than air and so tend to move downward while being mixed with surrounding air.

But ultimately the bilge is not completely sealed and there is some air exchange over time. The propane diffuses into the incoming air and its concentration gradually drops. Once in solution the propane does not settle out, that is, it does not form a highly concentrated layer at the bottom of the bilge.

Gasoline vapor is both heavier (well, more dense) and more explosive with a wider LEL-HEL range of 1.2%-7.1%. There are far more gasoline-powered boats (with engines below decks) on the water than boats equipped with propane systems. While bilge explosions do occur, they are infrequent considering the enormous number of craft and the comparatively lax standards of maintenance and operation that are applied on so many of them.

While propane is dangerous if handled carelessly, I think the risk is oft times exaggerated.

[Gypsyjon]

I would bet that it gets sucked into the engine while you are running and disappears. There is quite an air flow through the bilge, especially with a diesel engine. Even though it is heavier than air, the turbulence will no doubt stir it up and it will get used or blown out.

[boatman61]

I think any that 'gets away' before the burner ignites goes up at the same time.. that's why sometimes one gets that 'Woosh' as it lights if the first try fails..
Doubt if any gets to the bilge..

[BlackHeron]

Originally Posted by Jammer

Over time propane dissolves in air forming a solution. Between 2.1% and 9.5% propane this solution is explosive. Propane, and solutions of air and propane, are heavier than air and so tend to move downward while being mixed with surrounding air.

But ultimately the bilge is not completely sealed and there is some air exchange over time. The propane diffuses into the incoming air and its concentration gradually drops. Once in solution the propane does not settle out, that is, it does not form a highly concentrated layer at the bottom of the bilge.

Gasoline vapor is both heavier (well, more dense) and more explosive with a wider LEL-HEL range of 1.2%-7.1%. There are far more gasoline-powered boats (with engines below decks) on the water than boats equipped with propane systems. While bilge explosions do occur, they are infrequent considering the enormous number of craft and the comparatively lax standards of maintenance and operation that are applied on so many of them.

While propane is dangerous if handled carelessly, I think the risk is oft times exaggerated.

So basically it diffuses as it mixes with the air, but that takes a little time at first and it tends to settle to the bottom of the air in the boat before it can slowly mix evenly with the atmospheric air above it.

[sailorchic34]

Assuming 10 seconds of propane leaking before lighting (which is lots) and a 6000 btu stove top burner, you're looking at 0.00015 pounds of propane. After the burner lights the heat of combustion causes the air around the burner to be drawn towards the burner. More then likely the leaked propane is burned and consumed as air is drawn towards the burner.

Having lived aboard for 13 years now, it's never been an issue.

[Flextron]

Never been an issue. However, when sailing with the army in the old days from British Kiel Yacht Club. You had to make a log entry every hour and update you DR on a thing called a paper chart! At the same time the crew had to pump the bilge. The rule was pump dry them 10 strokes for gas! The instructor was wonderful Capt Ken Hazard!!!

[hellosailor]

I think it is Brownian motion, the random movement of the gas molecules, that eventually diffuses the propane into all the rest of the air in the boat, and since that is hopefully way below the explosive threshold, eventually the "not quite air" gets circulated out of the boat and the danger doesn't build.

With natural gas ashore, there is a distinct odor added to the gas so you can tell if something is leaking. (Methyl mercaptan?) I know I can "smell gas" but have never detected that odor, even in a closed room, after a stove or other gas appliance was lit. So I expect part of this is because very very little gas escapes before the flame, and much of that combusts with the flame.

[boatpoker]

I press and hold the igniter before I open the valve. Time to combustion measured in microseconds.

Quite comfortable that any gas in the vicinity of the burner is ignited.

[Sailshabby]

To add to the general consensus, keep in mind 100% if the excess propane isn’t rocketing into the bilge. Some, if not all, is being diffused and “carried” by the drafts found in your cabin.

[Brewgyver]

Assuming the spark igniter is working properly, I doubt that any measurable amount actually escapes combustion in the moment of ignition.
If you’ve never tried it, light your burner at night, with the cabin lights off. You may be surprised at the fireball that is invisible in higher ambient light levels. Even the steady burner flame will appear quite a bit higher in the dark.

[newhaul]

Ok propane released when you turn on a 6500 btu burner is .184 oz per second. So its really not enough to even think about. Besides it is usually consumed in the initial burn / just enough to fill the burner itself prior to ignition.