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.
A plenum chamber is a pressurised housing containing a gas or fluid (typically air) at positive pressure (pressure higher than surroundings).hese gave rise to the notion of 17th century 'plenum' as the opposite of vacuum, and all things being either Plenum or Vacuum. By the 19th century, the development of mechanical fans and industrial machinery had provided another, more technical use.