For instance, {HEAD ~ the next maintenance step} for {TAIL ~ the degas chamber 211A} may be after processing of 4000 substrates, while, for the degas chamber 211B, 7000 substrates can be processed 
for
For instance , { HEAD ~ the next maintenance step } for { TAIL ~ the degas chamber 211A } may be after processing of 4000 substrates , while , for the degas chamber 211B , 7000 substrates can be processed
OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH