In an old recipe collection book (1960) I have read the following on bbq
"Never Use Charcoal for Broiling
Charcoal absorbs great quantities of poisonous gases. It is used for this purpose in gas masks. It will absorb ninety times its own volume of ammonia gas. Most charcoal briquette contain quantities of wood alcohol and acetic acid. These fumes are given off as the briquette burn and are extremely toxic.