Lifetimes for the 4I13/2–4I15/2 transition of excited Er3+ ions in sodium di-silicate glasses have been measured as a function of Er3+ concentration and glass melting conditions. Lifetimes in excess of 20 ms have been measured for Er3+ levels up to 1021 ions/cm3. For Er3+ levels above 5 × 1020 ions/cm3 high lifetimes are only observed in glasses with low −OH impurity levels. The results are consistent with a quenching mechanism incorporating energy transfer between Er3+ ions followed by non-radiative decay via Er3+ ions coupled to the −OH impurity phonons.