The filter elements made of borosilicate glass fibers are used where micron/sub micron filtration (For filtering the contaminants with particle size ranging from 1 micron to 0.01 micron). The fibers of borosilicate form a mesh like network and the voids in this mesh affect the trapping of the contaminants (mainly in the form of oil mist, aerosol or vapour) because of this, Borosilicate fibers are classified as DEPTH FILTERS. The borosilicate glass fibers are inert and are resistant to all strong alkaline bases & acids. The fibers are also heat resistant and will soften only at temperature of 600?C and above. The retention capacity of borosilicate is very high because of very high void volume (96%) and has a very high holding capacity with a very low pressure drop.