What does VOC mean?

Volatile Organic Compound

Volatile Organic Compounds

In this case, the remnants of chemicals left from turning the wood to charcoal.  In wood fires, they are seen as the flames. When lump is made, most, but not all are separated and driven off from the carbon. They come off when the lump is still quite cool, under 400F I believe.

the VOCs aren't remnants of the fire we are cooking with, but actually from the process of making charcoal in the first place.  it's a minor difference, but it explains why there are VOCs in the charcoal even if you fire isn't lit.  and it explains why your fire (which is heat, plus a draft) can help drive out the VOCs early in a cook, so that your unburnt charcoal isn't still laden with VOCs later  at the end of a cook, or as the fire ignites new charcoal

to be ultra picky, "volatile" doesn't necessarily mean "flammable", just that they readily evaporate. 

So does that mean during a low temp cook at 250 vocs are present for entire cook?

perfume is perfume because it has volatile compiounds.  they are volatile precisely because they become airborne at essntially room temp.

the stink in a painted room is from VOCs.  opening a door and a window creates the same draft that your lowr and upper vent do.  the air washes the VOCs from the lump (or paint).  heat up that room, or the egg, and you almost literally boil off the VOCs even faster.

this is why unburnt lump loses its VOCs in an egg.  the VOCs aren't something burnt away, the fire just helps it happen quicker.

yes, there are VOCs 'locked' down in the lump, but the vast majority of the VOCs are blown off and so we don't get that 'bad smoke' smell three hours into a cook.  it's long gone.

smell it.  smells good, tastes good.