Occasionally, the reason for the high reading is that one of the compounds in the latest injection has not fully cleared, whether the compound was included intentionally or is a contaminant of some sort.  To remedy this, let the Mini GC clear out before the next test.

 

Another potential explanation (and a problem that the user cannot fix) is some compound that has irreversibly absorbed into the sensor film.  Unfortunately, such a compound may be a contaminant in an otherwise innocuous reagent.  If clearing out the column does not fix the issue, please email chemistry@vernier.com