  Luminosity outbursts of the FUOri type stars, which have a magnitude of
$\sim100 L_{\odot}$ and last for decades, may affect chemical composition of
the surrounding protoplanetary disk. Using astrochemical modeling we analyze
the changes induced by the outburst and search for species sensitive to the
luminosity rise. Some changes in the disk molecular composition appear not only
during the outburst itself but can also retain for decades after the end of the
outburst. We analyze main chemical processes responsible for these effects and
assess timescales at which chemically inert species return to the pre-outburst
abundances.
