COMO is using 2 scintillator materials. For the detection of alpha-radiation ZnS is used, 

for detection of beta and gamma radiation a plastic scintillator foil is used. 

The large area detector window is permeable for low energy alpha radiation like 238U, or beta radiation like 14C. The thin window can be replaced easily by the user and measurements can be continued without delay. 

The light flashes generated by the alpha or beta/gamma radiation can be separated by pulse analysis. 

The detected events are counted over time and displayed digitally in c/s, Bq or Bq/cm2. Nuclide specific sensitivity is calculated and alarm values are pre-programmed. 

Measurement results can be stored and transferred by RS 232 C.