An airbox 14 beneath chain grate 8 has {HEAD ~ a series} of {TAIL ~ airbox zones} 16, 18, 20, 22, 24, 26 and 28 extending serially from adjacent the input end to adjacent the output end, including a minority thereof adjacent input end 4 and a majority thereof remote from input end 4 
An airbox 14 beneath chain grate 8 has { HEAD ~ a series } of { TAIL ~ airbox zones } 16 , 18 , 20 , 22 , 24 , 26 and 28 extending serially from adjacent the input end to adjacent the output end , including a minority thereof adjacent input end 4 and a majority thereof remote from input end 4
OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH