The HVAC system was installed in the plenum space above the ceiling.
plenum duct
Frequency:
50
%
The plenum duct was leaking air, causing inefficiency.
plenum pressure
Frequency:
45
%
The plenum pressure in the ventilation system was too low.
Idiomatic Expressions for plenum
Phrase: plenum session
Meaning: a meeting or session attended by all members or participants
Usage: The plenum session was scheduled to discuss important matters.