Will my rocket oven explode if I start it?

Hi, I built a rocket oven out of barrels with my father. My father is a car mechanic and he is very... relaxed about safety.

I know that two of the barrels contained brake liquid (direct translation, hope you know what I mean?). It was all clear liquid, like water. He drained the rest and put his high pressure air hose in there before opening them and dried all the remaining fluids. He then cut them without any issues. I wasn't sure if they needed cleaning after, but he said I could just give them a good round of burning and the remains of whatever was in there will be gone for good. He also thinks nothing can happen because the liquid component is gone, leaving only whatever it dries out to be.

Now I'm not so sure. I haven't tried it out yet because.. you know, there is an almost closed chamber there that wasn't cleaned properly. My father is missing a few fingers because of his safety philosophies and is not usually building with barrels, so I thought I'd ask you before setting myself on fire. Is it safe for me to light it? I would clean the chamber containing the food very well, of course. But the chamber the gases flow into? I could maybe put some water in there through the chimney, but the barrels might get rusty, right? As it can't dry off properly?

That looks like a fun experiment.

My suggestion would be to take one of these mini torches that are used for browning foods in the kitchen and burn off any residue that might be inside.  Please use safety equipment like long gloves and glasses.

Maybe some of the more experienced folks will speak up with their suggestions.

I say this in the dailyish I thought you might enjoy this video:

Brake fluid is flammable but has a pretty high flash point. If it was cut with a torch without issue then there should be no issue. A small residual amount will not explode like gasoline.

Brake fluid isn’t clear so is it possible someone was already “cleaning” the barrel and maybe had water set in it?

Paul just released a new excerpt from the wood oven movie.  This one talks about barrels and has a bit of info on barrels : https://youtu.be/qiV-zKAyj6w

Brake fluid is a light hydraulic oil. It doesn't give off a flammable vapour. I don't think there is an explosion hazard, so I would go ahead and light it.

The stove will smoke the first few times from the paint on the barrels and the galvanized feed and exhaust tubing. Don't breathe in the fumes!

Thanks for your advice so far.

He cut all of the barrels with an angle grinder with lots of sparks flying everywhere (I think I can see where some of them went on the inside?) and welded them using gas shielded welding equipment (the very bright, very loud technique). If nothing started burning then, thats a good sign, right?

Below is me laughing nervously while shitting my pants about what we're going to do with those barrels.