I continue to see brothers posting that they are extracting both open blast and closed loop indoors without an engineered ventilation system.  Some arguing that they have done it for years with no issues.

LPG combustion requires fuel, oxygen, and an ignition source.  If we stay in control of any one of those, we won’t have an explosion.  In the case of open blasting or a closed loop system with a leak, we are relying on controlling the ignition source.

While we have control of electrical and pilot light ignition sources, we have less control over static electricity, from clothing sparks from a dropped metal object.

Let’s look at what happens when butane is ignited.  For starters, it only takes 1.9% concentration of butane in the atmosphere to reach Lower Explosive Limits.


The Lower Explosive Limits of Butane is 1.9% by volume

400 ml can of lighter butane

Flame temperature of butane in the atmosphere is 1703K/1430C/2610F.



400 ml = 24.4 in3

24.4 /.019 = 1284 in3 air fuel mix at LEL

1703K – 294K (ambient) = 1409 K heat rise.

1409/294 = 4.79 X

1284 in3 fuel air mix X 4.79 expansion factor =6150 cubic inches

Total expansion = 6150/24.5 = 252X

That 2610F air will be looking for a way to occupy the 252 X space it needs and pushes everything out of its way to get it.  That includes the roof, windows, and walls.

Consider that the largest non nuclear bomb in the US and Russia’s arsenals, often called MOABs, for Mother Of All Bombs, is an air fuel bomb.

The prime consideration of course is damage to people and animals.  Here are some purdy pictures of someone whose had that experience:

As you can see, it ain’t purdy and potentially involves significant pain and disfigurement.

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