Some other examples of gas sensing related to food safety or quality include: detection of gaseous amines, which are indicators of fish and meat spoilage, at the parts-per-trillion (ppt) level (theoretical) effected using fluorescence quenching of nanofibrils of perylene-based fluorophores or at the ppm level using conductance changes in composites of SnO2 nanoparticles and TiO2 microrods; a series of electronic sensors which utilize ZnO–TiO2 nanocomposites or SnO “nanobelts” to detect the presence of volatile organics, including acetone, ethanol and carbon monoxide; and WO3-SnO2 nanocomposites to detect the presence of ethylene gas, a hormone responsible for fruit ripening