The name is due to the double function performed by the component:
particle filter and anti-odour filter.
They are made ,by coupling to a filter element similar to the particle filter,
a second grains support element “Active Carbon “. The last one absorbs,
inside the grains, a part of the exhaust gas components to which
the man’s nose mucous membranes are particularly sensitive. Similarly
to particle filters, the characteristics of the filtering elements determine
a different filtration efficiency, with the possibility of removing dust particles
of different sizes (generally up to the size of a few tens of microns),
allergen agents (pollen or similar substances) and odors generated by
chemical substances of different origin (the exhaust gas of engines, industrial
smokes...).

They are made of non-woven fabric (non-woven), synthetic non-woven
fibers, preferably of polyester. Based on the characteristics of the filter
elements can keep the solid particles including dust, pollen, allergens
agents or similar substances of dimensions of a few tens of microns.