Rumford Fireplace Emissions Tests

Buckley Rumford Fireplaces
Rumford Fireplace Emissions Tests
9/18/23

The Rumford fireplaces all passed the emissions tests but the tests put the Rumfords at considerable disadvantage. See Rumford Fueling Protocol Rules.
When we tested with a fuel load proportional to the volume of the firebox - not the area of the inner hearth - and placed the fuel vertically as most people build fires in Rumfords, the results were spectacular - 2.4 grams of particulte per kiloghram of fuel (g/kg) when the passing standard set by Washington State was 7.3 g/kg. The current EPA Voluntary Fireplace standard is 5.2 g/kg.
So why was our Rumford so clean-burning and is that typical of all Rumfords? Can we come up with a design that anyone can build that assures clean-burning?

The reason Rumfords burns so clean is because the rounded airfoil throat combined with a straighr vertical fireback keeps the smoke hot and still burning behind a sheet of clean dilution air. The smoke is kept in the fire long enough to burn in the firebox wherte is contributes to useful heat rather than sent up the flue as pollution. See Rumford Fireplace Performance and an article in JLC that explores this further.
Is it typical? Rumford fireplaces have not been tested very often but the manuactured ICC Renaisance Rumford, which features the same rounded throat and plumb fireback gets excelent results burning open.
We think it's pretty simple to specify the Rumford design that anyone can build and burn clean. Round the throat, keep the fireback straight and plumb and the throat opening with a cross-section area of 1/20th of the fireplace opening cross-sectional area. That's pretty much already inscribed in the building code in Section R1001.6 Exception for Rumford fireplaces.