I always thought there was ash suspended in smoke. Too small to notice but gives the charcoal taste we know and love and gets in your hair, clothes. I have had BBQ that tasted "sandy", this was because I forgot to clean the grate. It didn't have any different taste apart from the unpleasant texture. My wife is freaking hooked on charcoal BBQ, we grill a fair amount; I'm a pyro too so I'm in charge of coal prep, it's an art for sure.