ZF TRW use the KIC reflow oven monitoring systems worldwide to ensure they have full traceability and control 24/7.
The KIC 24/7 system now superseded by the KIC RPI system, ensures the reflow oven profile is in spec. for every PCB reflowed.
Once a reflow profile has been created by passing a loaded board and reflow profiler through the oven, a suitable reflow profile is created.
Checking the oven periodically ensures the oven characteristics have not changed since creating the reflow profile.
But it is possible that the reflow profile is out of spec. for a period between checks, to avoid this the KIC RPI system checks the oven constantly and can score each PCB with a PWI value which indicates if the process is within spec. full traceability with no oven checks required.