{HEAD ~ The gas pressurization system} normally includes {TAIL ~ powered blowers} where a flap like sealing device can be installed to seal gas leakage 
normally includes
{ HEAD ~ The gas pressurization system } normally includes { TAIL ~ powered blowers } where a flap like sealing device can be installed to seal gas leakage
HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL REL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH