A negative air pressure plenum surrounds all contaminated positive pressure plenums. The valves connect the cylinder to separate steam and exhaust plenums. The aluminum plenums channel air from the air cleaner to the carburetors. They make parts such as piston kits, stroker kits, valves and Plenums. Plenums are the central distribution and collection units for an HVAC system. Henceforward, plenums, where grass-roots discussions and votings were held, took place in occupied lecture halls. The Congress was preceded by two exceptionally lengthy Central Committee plenums. The majority of speakers at Central Committee plenums were high-standing officials. Neither were plenums of the Central Committee held at regular six month intervals. Looking under the hood, one will notice a series of cast aluminum plenums.