In this article we will discuss about the physical and chemical techniques to control microbial agents present in air.
Important physical techniques are the following:
(i) Dust Control:
The dust particles are laden with large number of microbial agents that cause diseases and allergies. Since dust occurs in home, schools, factories, laboratories and hospitals, its suppression to lower down microbial content is, therefore, extremely important.
Use of dry-vacuum pickup followed by the application of suitable disinfectant detergents solution has strongly been recommended to control dust in indoor environments. In addition, oiling floors, bedclothes, and other textiles has proved a highly effective dust control device.
(ii) Ultraviolet Radiation:
This technique has great potential value for reducing indoor airborne microbial agents. Various types of germicidal lamps are used for this purpose. These lamps emit radiations in 250- 260 nm region, the most effective bactericidal region.
These radiations prove effective only when they come in direct contact with the particles laden with microbes; it is because these radiation have little penetrating power. Since these radiations are irritating to human eyes and skin, skilful installation of the lamps is required to avoid injury to persons using those rooms.
(iii) Laminar-Airflow System:
This is a new technique recommended for controlling indoor microbial agents. This technique represents unidirectional airflow system in which the air passes through high- efficiency particulate air (HEPA) filters and the entire body of air moves with uniform velocity along parallel flow lines.
The HEPA filters consist of cellulose acetate plated around aluminium foil and can remove particles as small as 0.3 µm. The laminar airflow system is, therefore, suitable device in electronic and aerospace industries where an extremely high degree of cleanliness is required for product reliability.
Indoor air-borne microbial population can be effectively reduced by vapourizing or spraying certain chemical substances into the air. Some of such chemical substances are propylene glycol, triethylene glycol, resorcinol, hypochlorous acid and β-propiolactone.
Polyethylene glycol and triethylene glycol are colourless, tasteless, non-irritating, and non- toxic chemicals. Nearly all microorganisms present in a liter of heavily contaminated air can be killed by vapour from only 0.5 mg of polyethylene glycol; triethylene glycol is nearly ten times effective in comparison to polyethylene glycol.
However, great care is required for safe and efficient application of chemical agents and, therefore, they may be used only when rapid control of air-borne microbial agent is essential.