The remote control system described makes it possible to install tracer gas canisters at selected locations in a modified in situ oil shale retort during rubbling. After rubbling, the tracer gas is released on command from the surface. These gas canisters are installed from the surface through existing retort access holes. Coded transmission is used so that the canisters can be triggered individually. The battery operated receiver with each canister can stand by for several months and then release the tracer gas when the appropriate signal is received. The proposed system would provide an economical method for obtaining tracer information.