The American black bear lived during the same period as short-faced bears (Arctodus simus and A. pristinus) and the Florida spectacled bear (Tremarctos floridanus). These Tremarctine bears evolved from bears that had emigrated from Asia to North America 7â8 ma.
A plenum space is a part of a building that can facilitate air circulation for heating and air conditioning systems, by providing pathways for either heated/conditioned or return airflows, usually at greater than atmospheric pressure.
Supply Air Plenums. 1  These supply air plenums are sheet metal boxes that attach to the outlet of a furnace or air handler and are used as a central manifold for other ductwork to connect to. 2  As the air blows from the furnace or air handler, it flows through the supply plenum and any ductwork attached to it. These sheet metal take-offs are designed to attach to a flat duct to allow you to connect round ducting to it. 2  They are used to attach your ducting to a supply or return air plenum. 3  Choose the size that matches the diameter of the ducting you will be using.