An air-to-fuel ratio in the combustion chamber averaging less than 35-to-1 as determined by the test procedure performed at an accredited testing laboratory.
A usable firebox volume of less than 0.57 cubic meters (20 cubic feet);
A minimum burn rate of less than 5 kg/hr (11 lb/hr) as determined by the test procedure prescribed in §60.534 of the U.S. EPA Federal Register and performed at an accredited laboratory;
A maximum weight of 800 kg (1,760 lb). In determining the weight of an appliance for these purposes, fixtures and devices that are normally sold separately, such as flue pipe, chimney and masonry components that are not an integral part of the appliance or heat distribution ducting, shall not be included.