A desulphurization event includes operating one or more emission control devices at an elevated temperature and with a selected air fuel ratio to reduce {HEAD ~ contamination}, such as {TAIL ~ sulphur} and other contaminants 
such as
A desulphurization event includes operating one or more emission control devices at an elevated temperature and with a selected air fuel ratio to reduce { HEAD ~ contamination } , such as { TAIL ~ sulphur } and other contaminants
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD OTH REL REL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH