  We explore a set of single-point chemical models to study the fundamental
chemical aspects of episodic accretion in low-mass embedded protostars. Our
goal is twofold: (1) to understand how the repeated heating and cooling of the
envelope affects the abundances of CO and related species; and (2) to identify
chemical tracers that can be used as a novel probe of the timescales and other
physical aspects of episodic accretion. We develop a set of single-point models
that serve as a general prescription for how the chemical composition of a
protostellar envelope is altered by episodic accretion. The main effect of each
accretion burst is to drive CO ice off the grains in part of the envelope. The
duration of the subsequent quiescent stage (before the next burst hits) is
similar to or shorter than the freeze-out timescale of CO, allowing the
chemical effects of a burst to linger long after the burst has ended. We
predict that the resulting excess of gas-phase CO can be observed with
single-dish or interferometer facilities as evidence of an accretion burst in
the past 10^3 - 10^4 yr.
