(under subclass 330) Smoking devices provided with means either (1) to exchange heat between the burning charge and/or the smoke and some fluid (usually air), or (2) to heat insulate the burning charge and/or the smoke.
(1) Note. The mere provision of elongated passageways, even though claimed as being for smoke cooling, where no heat exchange means is provided, are not placed in this group, but in subclass 200 and indented subclasses, and 216 and indented subclasses of this class.
