Sparks a-flying or How to catch yourself on fire.

A few years ago I was working in San Francisco under the freeway, for a company I won't mention. Their equipment yard was a huge gated lot, full of rusted, beat up looking dirt movers and cranes. You had to go into a bad part of town and I can remember that the drunks that lived in tents in the yard were fighting in the early morning. I was nervous about it, but it was only a one day job, and I had the company of a work buddy, so I figured I'd be safe.
The sun wasn't up yet, and the cool white light from the street lamps cast eery shadows. The cranes looked prehistoric, and angry. Early morning traffic still wasn't even stirring, I think it was 4am.
My buddy M, and I set up to work on the shovel of a Super 20, the teeth were missing and torn apart, they had really waited until the last minute to fix it. We fired up our generator (the drunks were mad about the noise) and I rolled out my cord for a 9 inch grinder. My job was to take the metal teeth all the way down, I followed behind M, who was air arcing off the teeth one by one. The smell of roasted CAT paint and burnt mud was just so disgusting I can't even explain it! I held my breath and got to work.
A nine inch grinder weighs around 25 pounds or more, and it can really wear out your arm if you have to hold it in awkward positions. It also has a truly gnarly kickback, and will grind through a pair of thick leather gloves in about one second. I was wearing my welding leathers; a long sleeved shirt with a high collar, to protect against the heat of working next to radiating hot metal. I also had on my welding hood, a hard plastic hat that shield your face, with a five inch by two inch glass window. This was because I was working along side someone Arc-ing ( if you don't protect your eyes you damage them) In the window you attach the "lens" which means you either have a fixed dark lens and have to flip up the hood to see anything and flip it back down before you strike and arc. The fixed dark lens is so dark that you can hold your hand right in front of your face and still not see it- welding creates light that is something like 2-3 times the strength of the sun (totally inaccurate, but something like that). A more expensive alternative is a "quick change lens" which mean that until it senses an arc ( some meer fraction of one second and it darkens) its totally see- through. I have one and it cost me 300$. Not cheap!
So there is a reason I explain all this, I had the hood on, and I couldn't see too good. The sparks were flying back onto the leather apron, because I couldn't see where my sparks were going (you can aim them if you can see). Well all the sudden I smelled this strange smell. I stop working, I sniff. I think, hmmmmm? I look down and see red flames! I'm on fire! I roll into a puddle of filth and my buddy is slapping me with his gloves to put me out. So finally I get up; I stink like urine and grease, my sweat shirt has a huge hole in it, I'm wet, I'm extremely embarrassed. I go back to work. Some things you just don't live down.