The monoxide carbon
is produced by the incomplete combustions, as for example the emissions of the internal combustion engines that are the major cause of
the diffusion of this polluting. In fact if it is produced by the chimneys
of the houses or factories it doesnt
fall onto the soil because it has the same the density of the air, therefore it becomes dangerous for our health only when it is
produced by motorvehicles which emit it to the height of a man. In Perugia this polluting substance is present beyond the
espected limits while, in the period taken into consideration, it is not present in Terni. 