What are Parallel Fan Powered Variable Air Volume (PFB-VAV) systems?

A single air handler which provides central cooling, ventilation, and sometimes central heat to multiple ducted zones.

Each zone has a local (primary air) damper that opens and closes to allow cooling and recirculation air into the space.

All or some zones have a local reheat and a local fan that pulls air from the plenum (secondary air) through the reheat and back into the zone to heat the space.