The diamond NPs behaved differently from the other carbon NPs in two seemingly contradictory ways. On one hand, the diamond initial EEO2 values were five to ten times lower than those for the other NPs, but the diamond NP were also the only ones for which EEO2 never dropped below 10 -5 Da/O2 collision. The low initial reactivity is attributed to these NPs having been pre-heated prior to the start of oxidation, so that they had already partially evolved, and the failure to become completely inert is likely due to the fact that these experiments were done at 100 to 200 K lower TNP than the others, which probably slowed the continued evolution of the NPs. Figs. 1B, 2 and 3 show that diamond NPs can have EEO2 comparable to other carbon NPs, and do become inert if the experiments are run at higher TNP.