New Product Release

March, 2009 – Test results show that the WoodMaster Plus outdoor furnace, developed by Northwest Manufacturing of Red Lake Falls, Minn., produces an average emissions rate below the new volunteer standards set by the U.S. Environmental Protection Agency (EPA). The WoodMaster Plus furnace is on display at the 2008 Hearth, Patio and Barbecue Expo.

The EPA announced new emissions test guidelines on January 29, 2007, as Phase 1 of its Outdoor Wood-fired Hydronic Heater (OWHH) Program to promote manufacturing and sales of cleaner outdoor wood furnaces.

The EPA Phase I OWHH Volunteer Program emissions standard is 0.6 lbs/million Btu heat input. The EPA Phase 2 OWHH volunteer program performance level is .32 lbs/million Btu heat output. 

In testing, the WoodMaster Plus produced an average emissions rate of:

0.10 lbs/million Btu of input for the heating season

0.11 lbs/million Btu of input for year round

Intertek Testing Services NA Inc. (Intertek), an EPA accredited laboratory, conducted tests on the WoodMaster Plus furnace in November – December, 2007 at its Middleton, Wisconsin, laboratory. Tests were evaluated to the ASTM Proposed Standard Test Method for Measurement of Particulate Emissions and Heating Efficiency of Outdoor Solid Fuel-Fired Hydronic Heating Appliances.

The testing process included four runs with four hours of burn time each, fueled by hardwood pellets. During each run, the cooling water for the heat exchanger was set to draw these four different output rates: 100,000 Btu/hour, 50,000 Btu/hour, 25,000 Btu/hour and 15,000 Btu/hour. Minor adjustments were made to maintain the heat exchange rate. The water-to-water heat exchanger was adjusted for each of the heat loads by increasing or decreasing the water flow through the cooling side of the heat exchanger.

About WoodMaster and Emissions

For hundreds of years, Americans have burned wood as a primary source of heat. WoodMaster, Northwest Manufacturing and other responsible manufacturers continually work on proper installation so outdoor furnaces produce clean, safe heat.

The U.S. Environmental Protection Agency (EPA) says: "Compared to a wide range of residential heating options, these furnaces' emissions were of the same order as other stick wood burning appliances." (EPA report: EPA/600/SR-98/017, February 1998)

HPBA and EPA Phase 1 Emissions Guidelines

Through the Hearth, Patio, Barbeque Association (HPBA) association, WoodMaster's developer, Northwest Manufacturing, has worked closely with EPA on new testing standards and works with state and local governments on appropriate regulations to encourage cleaner burning outdoor wood furnaces.

The test standard used for testing the Northwest Manufacturing, Inc. model AFS900 Pellet Fuel Outdoor Hydronic Heater (WoodMaster Plus model) is not a published test standard and is currently in a draft status. Results from this testing cannot be used for certification unless the draft standard is published without change. The use of these results in advertising that includes the name of Intertek Testing Services NA, Inc. or Warnock Hersey will require written authorization by Intertek before it is published.

WoodMaster and WoodMaster Plus furnaces are developed, manufactured and marketed by Northwest Manufacturing, a privately-owned company based in Red Lake Falls, Minnesota. The company offers a range of furnaces to heat homes, garages, pools and spas; under floor heating systems; and replacement parts for all outdoor furnace brands. For more information about the company and its products, visit