The relative humidity is an important factor that can affect the efficiency of the filter.

A relatively high temperature can even generate desorption, with the filter releasing previously adsorbed gas molecules. Generally, the temperature must be kept below 40☌.

This is especially true for gases with a low boiling point.

The higher the temperature of the gas, the lower will be the adsorption capacity.

The impregnation of filter media can greatly extend the range of gases that can be removed from the air stream.

This is a chemical reaction in which the two substances react together and the resultant chemical is trapped on the filter material.

The physical process of adsorption is followed by chemical adsorption (chemisorption).

This represents a surface area roughly equivalent to about 4 football fields. Depending on the carbon is use and the type of filter, the aggregate surface area is in the range of 2000m 2/g.The specific surface is a measure of the surface area per unit of weight, which is m 2/g.The number of pores present in the carbon is vast and therefore the total surface area is extremely large.

Attracted and captured in the space by the Van Der Waals’ force, the molecules penetrate into the pores, impact the walls and are trapped.The gas molecules move into an empty area and diffuse into the pore.Adsorption of the gas molecule is by diffusion (Brownian Movement) or adsorption/condensation using Van Der Waals’ forces. Two main processes by which adsorption takes place are physical adsorption and chemisorption. The filtration of gas molecules is based on the concept of adsorption.

Carbon filters