Abstract: Methods and apparatus for burning a mixture of natural gas and air in a ratio that is slightly fuel rich to slightly fuel lean with substantially minimal emission of gaseous pollutants containing nitrogen, hydrogen, or carbon. The mixture is provided along a predetermined path in a non-radiant burner and is ignited to provide a blue flame in a predetermined burning region. A refractory porous member located in the cool region adjacent to the upstream end of the burning region reduces the temperature of combustion slightly by scavenging a substantial fraction of the excess free radicals that are critical to the formation of nascent NO and its conversion to NO.sub.2 and the nitrogen acids. Typically the porosity in the porous member is about 92 to 97 percent and its thickness is such that it extends into the flame to a level at about 25 to 50 percent of the height of the flame. The mixture typically comprises about 80 to 120 percent theoretical air.