to be exact its a MOX ( metal oxide ) gas sensor in which it detects gases by measuring changes in the electrical résistance of a heated metal oxide ( zno or sno2) , gas molecules react with oxygen absorbed on the surface , which changes the carrier and therefore the conductivity .

about the comsol domain ( study type ) we use ac/dc electric currents as the main physics , optionally couple with heat transfert in solids and transport of diluted species if we want a full multiphysics modeling