{HEAD ~ An airbox} 14 beneath chain grate 8 has {TAIL ~ a series} of 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 
{ HEAD ~ An airbox } 14 beneath chain grate 8 has { TAIL ~ a series } of 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
HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH 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 OTH OTH OTH