  A new type of object called "Very Low Luminosity Objects (VeLLOs)" has been
discovered by the Spitzer Space Telescope. VeLLOs might be substellar objects
forming by accretion. However, some VeLLOs are associated with strong outflows,
indicating the previous existence of massive accretion. The thermal history,
which significantly affects the chemistry, between substellar objects with a
continuous low accretion rate and objects in a quiescent phase after massive
accretion (outburst) must be greatly different. In this study, the chemical
evolution has been calculated in an episodic accretion model to show that CO
and N2H+ have a relation different from starless cores or Class 0/I objects.
Furthermore, the CO2 ice feature at 15.2 micron will be a good tracer of the
thermal process in VeLLOs.
