Made in the USA, the Creosote Control Brick reduces the risk of chimney fires by helping to prevent creosote build-up. Each tightly compressed firebrick contains special chemicals that help slow creosote buildup; helping to prevent chimney fires and extending the time interval between cleanings. It contains no waxes or oils and is safe for use in all wood burning appliances. Made from Douglas Fir and Western Red Cedar it burns like cordwood. Complies with California Proposition 65. Each pack contains 4 treatments. Treatment times depend on your appliance and burn frequency ranging from 1 treatment every 6 weeks to 2 weeks. A treatment is recommended for fireplaces every 30 fires. For woodstoves and inserts, a treatment is recommended every 6 weeks if only burn during weekends, every 4 weeks if you burn 1 fire per day and every 2 weeks if you burn a continuous fire.