Certain materials useful in space sensor construction were tested for their noncontaminating compatibility with channel electron multipliers. Gain profiles indicate that the materials tested do not adversely affect the lifetimes of the multipliers. These materials are, therefore, shown to be safe for use with channel electron multipliers in space instrumentation even for the most stringent long lifetime mission requirements. The tests indicate that the multipliers which are to be flown on an extended space mission will have adequate lifetimes to return satisfactory data throughout the entire mission.