Wood smoke can also be produced by
blowing a stream of hot air or air/inert gas
mixture countercurrently across a bed of
sawdust that is being fed at a controllable rate
into a fl uidization chamber that has the form
of a truncated cone (Nicol 1962 ). The temperature
of the fl uidized bed of sawdust or chips of low mesh size is kept below 400 ° C
to prevent self - ignition. The composition of
the smoke can be controlled by modifying
the content of oxygen in the air mixture. Self -
ignition of the fl uidized sawdust bed may be
prevented even at a temperature as high as
750 ° C if the concentration of oxygen in the
gas mixture is reduced to 6% (Balejko and
Miler 1988 ). The quality of the smoke produced
in a fl uidized bed at such a high temperature
is equal to that from a smoldering - type
generator.