Boman reports that temperatures above 850°C, in a 5kW combustion zone combined with air rich and well-mixed conditions for 0.5 seconds in the post combustion zone, resulted in an almost complete depletion of particulate matter (Boman et al., 2005).

How can we achieve 850°C in a combustion chamber? 

Yellow flames are around 1,100°C. but: 

1. Heat flows in one direction, from hot to cold.
2. Mass, charcoal, and incoming air (primary and secondary) are usually much colder.

Elevating temperatures to 850°C in the combustion chamber is not easy but it is possible!

1. Use a thermometer.
2. Create hot fires.
3. Reduce mass as much as possible.
4. Replace mass with insulation.
5. Inject pre-heated air into charcoal to create high temperatures, especially in the top of the pile. Charcoal is a good insulator and when the top of the fuel bed is not red hot the effect can be cooling.
6. Minimize the pre-heated incoming air, maintaining a minimum 3 to 1 fuel/air ratio.