“To apply controlled atmosphere there are several techniques available on the market. The reader should be aware that Controlled Atmosphere is a broader and more advanced method than techniques that solely focus on lowering the oxygen level in a “controlled” environment.”

Nico Vroom Control Union, Netherlands Controlled Atmosphere Specialist Controlled Atmosphere means controlling insects by maintaining low levels of oxygen in a gastight environment (room, silo or container). The Controlled Atmosphere treatment (= low oxygen levels) is created by a converter system, constructed by specialist engineers, and a gastight environment e.g. a room or silo. (fig 1.).

The converter system and the room/silo are connected to each other and form a closed circuit. Low oxygen levels vary between 0.5% and 1.0%. It can be applied in airtight environments ranging from 1M3 to 1000 M3. Insects in all stages are eliminated (99,996% Lt) because of the lack of oxygen which causes the insects, larvae and eggs to dry out and suffocate.

The infected products are exposed to CA in airtight climate rooms equipped to handle variable sorts and quantities of products such as grains, cereals and flour specifically. The temperature, oxygen and humidity are controlled in each room within a specified range of parameters known to be lethal to the specific pests. The treatment normally requires 1 to 6 days, depending on the type of infestation & (product) temperature. The treatment is fully automated and can be initiated, monitored, managed and halted online by computer if required.

TOOLS & METHODS To apply controlled atmosphere there are several techniques available on the market. The reader should be aware that Controlled Atmosphere is a broader and more advanced method than techniques that solely focus on lowering the oxygen level in a “controlled” environment.

With Controlled Atmosphere, parameters such as nitrogen, oxygen, moisture and temperature of air and product are fully in control because of the use of computerised equipment.

This full control of the parameters makes it possible to apply a tailor made treatment of a certain product/insect/packing/temperature combination. Not only resulting in 100% effect and the lowest treatment time but also in safeguarding the product quality.

Tools Most commonly a basic machine that can establish a Controlled Atmosphere in an enclosed environment is used, which is the oxygen converter machine. This type of machine separates the oxygen from the air by separating some species from a mixture of gases under pressure according to the species molecular characteristics and affinity for an absorbent material. A schematic view of how the CA is working inside the gastight environment is showed in figure 2.

Methods The techniques are applied via various methods, all suited for the specific variable set-up of circumstances. In this sub paragraph the main methods are described.

Please be aware that between technique and method there are a lot of complex steps of mechanics, electronics and operating procedures that play their part in effective pest control with the use of the CA Technique.

Controlled Atmosphere Rooms As described the CA technique can be applied via several methods, depending on the circumstances. A lot of products which are infested with insects are packed in boxes, big bags, and crates etc. that are stacked on pallets. These wooden or plastics pallets can be easily driven with a forklift in an airtight room which is sealed with a special door.

These rooms are normally constructed within a warehouse, sometimes used to create a “clean” and dirty “zone” with doors on both sided of the room.

In some conditions where there are facilities that are influenced by season patterns or the equipment is used within an agricultural cooperation, a containerised system is used that is suited to transport from one location to the other.

Silo Treatments Most of the grains and other agro bulk commodities are stored in silos. Although there are a lot of types of silos, CA can be applied to all of them (as long as there is the possibility to create almost airtight environment).

Insects Extensive databases of products, insects and treatment parameters are used to create the most accurate atmosphere for each specific treatment. Always the right method should be chosen, in a way that the treatment is safe for the product, lethal for the insect and cost effective in time and money.

As mentioned before; the insects dry out and suffocate from the lack of oxygen. CA is most effective in time when the product itself has a higher temperature. If the temperature of the product at start of the treatment is low, temperature can be automatically increased to any desired level which is safe for the product and cost effective in time and money.

The higher the temperature level of the product; the shorter the treatment time. Figure 3 show you an example of the treatment times for the most common insect on Tobacco products:

The first big scale CA treatment terminals where constructed in The Netherlands and Belgium in the beginning of the millennium, this on initiative of the National and European Government in cooperation with commercial partners. Currently there are hundreds of treatment rooms around the globe and used frequently in the milling industry.

An important fact in the development of CA is the new registration of phosphine in the EU (already in Germany, soon approved in the UK and then in all countries), contains a quarantine period to follow each traditional fumigation, when the product cannot get into the next step of the production chain.

For example grains and rice must be kept for at least 7 days after a fumigation before they go to a mill and the same may go for the final product. This delay gives a huge advantage to CA as the prefered solution for keeping the high quality of milling supply chains.