Toxic substances have so far been used in the process of disinfestation of foods but these toxic substances are coming in for increasing stronger criticism. Substances like Methyl Bromide, Hydrogen Phosphide etc. also face the problem of residues seriously. Therefore, researches were undertaken to substitute and supersedes such chemicals with natural reside-free and environment friendly disinfestation processes.

In the new process of fumigation, the originally packed agricultural product is exposed to pressurized CO2 atmosphere. The infestation is done on the optimum condition and cycle time of few hours is required of the product that has to be fumigated. No special pre or post treatment is necessary. Product are takes to a special enclosure is flooded with gaseous CO2 to the required final pressure and the subsequent takes place in another vessel.

By avoiding the use of the so far commonly employed poisonous gases with a procedure of pressure disinfestations with Carbon Dioxide (CO2), the procedure is environmentally compatible and thereby eliminates the problems of residues.

The post harvest loss of food grains during storage or transport continues to be a serious problem. The last decade witnessed a great imbalance between the improved technology to enhance the crop production and dearth of effective post harvest technology to protect the harvest grains from insects, mites, rodents, fungi and bacteria unit it reaches the consumer. In fact, more than 4.0 million tonnes of food grains is lost per year and the cost to the economy due to this loss is enormous.

Therefore construction of sophisticated structures for grain storage and transportation, equipped with during, aeration and fumigation facilities the most important element in a strategy to save food grains.

Today, chemical pest control and other traditional methods of food grain preservation are becoming unacceptable for the reduction of post harvest losses for reasons of health hazards, ecology and economy.

CO2 is usually stored in its liquid state in low pressure vessel and is evaporated for use individually applicable. Gas Lab Asia has developed vaporizers to reduce costs for CO2 vaporization. These are of following types:-

In this, ambient air that is available at no cost is used and thus considerable energy saving is achieved as compared to the electric vaporizers. Installation can be done easily as the vaporizers are supplied in one unit ready for use. These consist of a special heat exchanger with copper tubes and aluminum blades.

Fin vaporizers consists of two or more finned aluminum elements, manifold together around seamless S.S high pressure tube and mounted vertically. Each element features eight fins that provide high capacity performance and faster defrosting. Standard element heights have approximately five sq. ft. of external heat exchanger surface per ft. of length obtaining maximum surface per liner foot.

There are no moving parts and no additional power or utilities required. These units are especially economical and maintenance free, yet highly efficient for vaporizing gases or fluids.

Air cryogenic vaporizer has element spacing substantially greater than convectional; natural convection ambient vaporizers and therefore permits continuous operation without defrosting characteristic of convectional units.

Wherever steam is available at the site e.g with bottlers, breweries etc., steam evaporator is a very cost effective system of evaporation of liquid CO2. Steam heated vaporizer is a twin tube heat exchanger. Liquid CO2 is in the center tube and steam is in the shell.

Steam evaporator eliminates the use of expansive electrical energy, which is required on other types of evaporators. The principle behind working steam heated vaporiser is that the sensible heat of steam is used to vaporise liquid CO2 and the condensate is automatically removed. The capacity of evaporator can be designed to most sufficient heat transfer. Shut off valves, safety valves reduction valves and filters are provided to ensure trouble free working of the equipment. Steam trap is also provided to economize on the consumption of the steam and automate removal of condensate.

Here, air (atmosphere) is blown into the set of finned tubes through which liquid CO2 is circulated for evaporation. Two sets are generally used. When one is used then it gets forested due to low temperature of liquid CO2 starts evaporating. The previously used tube gets ready once again. By this process, change over takes place at regular interval. This process continues to give continuous stream of evaporated CO2 gas.