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.
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. These return air plenums are the ducting that attach to a furnace for the return air to flow through, and are used as a central manifold for other return air ducting. 2  These sheet metal transition kits are used to make a custom fabricated duct to connect a new furnace or air hander to existing ductwork.