Did You Know?
The opposite of a ‘vacuum‘ is a ‘plenum‘
The term "plenum" derives originally from classical theories and the notion that "Nature abhors a vacuum". These 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. This referred to "a system of artificial ventilation", which used a pressure raised slightly above atmospheric pressure, in contrast to the "vacuum system" which used a pressure below atmospheric. At a time when high pressure steam or hydraulic systems were well established, these were a distinct set of systems based on low pressure and high volume flows.