O2 attack at defects in graphite basal planes results in etching at increasing rates as carbon removal enlarges the defects into etch pits. Thus, we might expect that NPs with passivated surface layers would regain reactivity and quickly etch away, if they become too defective. For the relatively low temperature conditions of maximum O2 etching reactivity, passivated NPs remained inert to O2 even though sublimation resulted in continuing slow carbon loss. Part of the motivation for the current experiments was to examine the effects of changing the oxidant, the oxidant pressure, and TNP on the balance of rates responsible for the transition from active etching to passivation, and to examine whether sublimation of carbon from the NP surface could reactivate NPs toward either O2 or N2O.