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.
Plenum spaces provide two problems if there is ever a fire. First, by necessity plenum spaces are loaded with fresh oxygen. A small, smoldering fire can really take off if it breaks into the plenum space. The second issue is that the air in the plenum space is forced throughout the whole building.