When the exposure period is ended the treated commodity should be left aerated for a certain time. Then the concentration inside the commodity will be detected to ensure that the fumigant left is not harmful to any person. If so, the fumigation period is over. Sorption Before a constant concentration of the fumigant can be maintained the sorptive capacity of the article under fumigation must be satisfied. It varied considerably with the article being treated.
Sorption includes the terms adsorption, absorption and chemisorption.
Adsorption is concerned with the loss of fumigant due to adhesion of impingement of the gas molecules to the surface of the materials under treatment. Absorption is concerned with loss of gas within the commodity due to capilary forces. Chemisorption is a chemical reaction that takes place with a gas and commodity. The process is irreversible. When chemisorption occurs, residues are formed.