We've got neighbors that ignore or don't know they're not legal. They use them all the time & it makes it hard for those of us downwind. We can't even open our windows on nice days.
If you have no neighbors downwind, it's ok to use wood. If not, be sure that they're legal where you live. There's an Ace Hardware about 10 blocks from me that sells the rings, but they're illegal to use within the city limits.