Infrared studies of hydrogen-deuterium exchange in bulk fused silica indicate that the rate of exchange steadily increases with temperature from 600 to 1000°C. The exchange takes place on isolated OH groups and occurs in either direction.
D. L. FRY, P. V. MOHAN, and R. W. LEE, "Hydrogen-Deuterium Exchange in Fused Silica," J. Opt. Soc. Am. 50, 1321-1321 (1960)