The oxygen partial pressure around a molten silicon drop was determined from the inlet (P-O2(inlet))and outlet (P-O2(exit)) pressures of a furnace under precisely controlled gas flow rate. It was found that P-O2(exit) is much lower than P-O2(inlet) and that measured P-O2(exit) depends on gas flow rate, but P-O2(inlet) does not. This dependence can be explained by an oxygen transfermodel using the Peclet number.