Man drops firecracker into grease pit - GIF

[Frank S]

But, Frank S., why wouldn't a fuse set off LP gas before the "firecracker" went off? I don't think "firecracker" is an apt descriptor of whatever he dropped into the pit.

The same reason it sometimes takes the electronic spark a dozen times to light a stove, BBQ grill or a space heater where as a match will light them quickly. or a lit cigarette with an ash in the end might be extinguished in a pail of gasoline but one with a glowing end will cause the vapors to explode its the size of the heat source and the concentration of the vapor molecules
For the firecracker descriptor, you could be partially correct, a M80 will destroy a large rural mailbox but will only deform or possibly split a sealed steel trashcan with the lid on tightly. A hand grenade could possibly displace a few of the timbers covering the pit but not to the level of the demonstration plus there would have been the danger of the shrapnel to the fool sitting in the chair.
Admittedly my explosives experience is based on limited training from 50 years ago but my vote still goes to some form of heavier than air volatile vapors and a large engough heat source to ignite them, for all we know they may have practiced this several times without the guy sitting in the chair before they felt they had a perfect combination

[WmRMeyers]

I bet his mama is real proud

She sees that, I bet she denies being his mama.

[hemmjo]

дебил = Debil

The word can refer to stupid or slow in many slavic languages including bulgarian, serbian, slovakian, russian and polish.

In spanish it means slow or weak, stemming from latin debilis which means feeble or weak.

On ogromnyj debil = he is a humongous idiot

Es muy débil de carácter = she is very weak

[NortonDommi]

дебил = Debil

The word can refer to stupid or slow in many slavic languages including bulgarian, serbian, slovakian, russian and polish.

In spanish it means slow or weak, stemming from latin debilis which means feeble or weak.

On ogromnyj debil = he is a humongous idiot

Es muy débil de carácter = she is very weak

Obviously you are not a moron.

[old kodger]

In my workshop he would be both metaphorically and physically FIRED.