Some experiments were designed and performed in order to elucidate the mechanism of re-volatilization in silica traps using flame AAS. A water-cooled U-shaped silica trap and a slotted silica tube trap were used, while organic solvent aspiration was employed for re-volatilization. Analytes were Bi, Au, Mn, Cd and Pb. The detailed experiments have shown that heating is not necessarily associated with re-volatilization: however, a direct contact between flame and active silica surface is required. The effect of the critical C/O value in the flame was also investigated and found to be important.