This is a summary of wood stoves certified by the United States Environmental Protection Agency (EPA) according to the latest list published September 22 2011 (http://www.epa.gov/burnwise/choosing.html). An EPA certified wood stove or wood heating appliance has been independently tested by an accredited laboratory to meet a particulate emissions limit of 7.5 grams per hour for noncatalytic wood stoves and 4.1 grams per hour for catalytic wood stoves. Tighter limits apply in the state of Washington - 4.5 grams per hour for non catalytic wood stoves and 2.5 grams per hour for catalytic wood stoves. For information on the the different types of woodstoves see http://www.epa.gov/burnwise/woodstoves.html. All wood heating appliances subject to the New Source Performance Standard for New Residential Wood Heaters under the Clean Air Act offered for sale in the United States are required to meet these emission limits.
These particulate emission rates are values obtained under controlled conditions in test laboratories. In real-life use, emission rates will be higher and depend on operator use, maintenance, and age of the woodstove. In a http://www.epa.gov/nrmrl/pubs/600r00100/600r00100.htm of the log-term performance of certified woodstoves by the EPA, it was found that actual emission rates were on average 175% worse than the certification value - see http://burningissues.org/car-www/science/epa-ws2-study.html. For the catalytic stoves, the average emission rate was 12.35 g/hr (9.88 g/kg), and for the non-catalytic stoves the emission rate was 15.90 g/hr (13.35 g/kg).
The graphs below show the distribution of certified woodstoves in each type - non-catalytic, catalytic, and pellet stove - from the list of certified stoves. A small number in the list have emission ratings greater than the limits stated above.