I use aromatic candles in my therapy room but keep it well ventilated. Talking of cheap and expensive, it's not the case that all cheap ones are rubbish and environmentally-friendly or vice versa. Those that are bad send off black fumes and I've had some relatively expensive ones that do that. Favourites at the top of the price range Diptyque, and lower down the scale Joseph Sandall, London Lily, The Amber Collection and Valennte. Valennte especially are really good value, a small husband and wife company and totally eco-friendly. I don't like candles with three wicks as invariably they leave a tunnel as the wicks burn down meaning a great waste of wax, and those with wood wicks that crackle I find tend to give off unwanted smoke.