The NFPA requires a fireplace insert to cover the entire length of the chimney when the fireplace flue cannot be 3 times the size in square inches of the appliance, fireplace or stove and 2 times the size in square inches of the exterior chimney. If these regulations are not met the entire length of the chimney must be lined.
The Environmental Protection Agency began regulating fireplaces and fireplace inserts and the amount of particulate emissions they emit. EPA certified fireplace inserts reduce the amount of particulate emissions from an appliance by around 90 percent, according to the Hearth, Patio & Barbecue Association.
The sale or purchase of new wood burning fireplaces and equipment that is not certified by the EPA is illegal in the U.S. Local air quality agency bans on wood burning on days of poor air quality do not affect fireplaces and stoves with EPA certified inserts.