Abstract: A system is presented for remotely measuring a concentration of a target material (e.g., radioactive gas, suspended aerosols or non-radioactive gaseous chemistries). The system includes a data processing system and a monitoring device. The device includes a detector having a chamber, collector in the chamber and a sensor. The target material enters the chamber. The collector collects ions generated by decay of the material. In one embodiment, the sensor measures changes in an electrostatic potential of the collector in response to the ions. In another embodiment, the sensor includes a scintillation counter that measures alpha or beta particles and provides an energy spectrum. In another embodiment, the sensor includes a material whose optical properties vary according to fields formed within the sensor. The device includes a transmitter for transmitting the potential, the spectrum or the field strength to the processing system for determining the concentration of the target material.