The main goals achieved by following all safety procedures related to product mixing
and loading that appear on every pesticide label are the protection of the health
of pesticide handlers and the prevention of environmental contamination.

Often, it is wise to consider additional tactics that will increase the probability of preventing harm to humans and the environment. One such tactic is the utilization of closed pesticide mixing and loading systems. These systems are designed to make it difficult for the concentrated pesticide from coming in contact with either handlers or the environment. Some pesticides require the use of closed mixing and loading systems due to the high acute toxicity of the particular product.

Mechanical Closed Systems
Mechanical closed systems are usually a series of various interconnected types of
equipment that allow you to remove a pesticide from its container, rinse the container,
and transfer the pesticide and rinse solution to the application equipment without being
exposed to the pesticide. The most common mechanical closed systems are only for use with liquid pesticides. Mechanical closed systems are usually either suction fed or gravity fed.

Mechanical closed systems are usually custom made to fit the needs of the type of
operation in which they are being used. One example is the use of higher volume pumps for aerial applicators who may be loading multiple aircraft and need to minimize the time for filling the mixing tank with diluent and loading the pesticide mixture into the aircraft-holding tank. The type of pesticide container, whether a mini-bulk, drum, or jug, can determine how the pesticide evacuation and container rinse systems are designed.

Suction System
Suction systems actively remove the pesticide from the container through a probe
inserted into it and by suction created by the pumping system. Some pesticide containers designed to be used with a suction system have the probe already built in. Once the pesticide container is empty, the probe system and container are rinsed with water, which is added into the mixing tank with the spray solution.

In a case where only a portion of the contents of the pesticide in the container
is used, the system must have a meter to monitor the amount of product that has been added to the mixing tank. There also must be a way to remove the probe for rinsing before the spray operation is concluded or another pesticide is metered into the tank prior to application. In some systems, the head of the probe remains in the container, while the remainder breaks away for rinsing.

One of the drawbacks of a suction system is that some pesticide containers with unused product in them will not be able to be resealed properly. Also, the pesticide must have a viscosity that will allow proper handling of the product. Those pesticides with high viscosity (tend to pour like molasses) may be more difficult to handle with a suction system.

Gravity System
In a gravity system, the unopened pesticide container is placed in a chamber that is sealed tightly to prevent spillage. A punch inside the chamber punctures the container,
thus allowing the contents to drain by gravity into the mixing tank. A water nozzle attached to the punch sprays enough water to thoroughly rinse the container with the
resultant rinsate being added to the final mix in the tank. Afterwards, the rinsed container is removed for disposal as instructed on the product label.

An advantage to gravity systems is that they could be designed for use with dry products, if the packaging is made of plastic. A limitation of this system is that only full container quantities can be added to the mixing tank. It is impossible to use only part of a container and store the rest.

Soluble Packaging
A much simpler closed-system for mixing and loading pesticides is soluble packaging. In this system, the pesticide container is designed to be placed unopened directly into
the mixing tank. The container dissolves in the solvent and releases the pesticide into the mixture. The most common solvent for this type of soluble packaging is water. Generally, the actual soluble portion of the container will have outside packaging that is water resistant to prevent potential release of the product before mixing takes place.

As with a gravity system, the entire contents of each soluble container must be added to the mixing tank at once, also making it impossible to add only a portion of the contents. Care must be taken at all times during shipping, storage, and handling to prevent any water from contacting the soluble container before mixing is initiated.

Personal Protective Equipment Considerations

Occasionally, the personal protective equipment requirements for many pesticides may be reduced if closed pesticide mixing and loading systems are available for use by handlers. Of course, the instructions relating to personal protective equipment on the pesticide label is the final word on any such reduction of requirements. Some pesticide instructions will allow for the substitution of personal protective equipment required by the label for regular mixing and loading with a long-sleeved shirt, long-legged pants, shoes, and socks. At times, the wearing of a chemical-resistant apron and gloves may be required for handling concentrated pesticides in conjunction with
closed systems. If the system is under pressure, protective eyewear may be required.

It should be noted that if label instructions allow for the use of less personal protective equipment when utilizing closedsystems for mixing and loading a pesticide, you should have all of the personal protective equipment required for regular mixing and
loading available at the site. This will be needed in the event of a breakdown of
the closed-system equipment.

Gary K. England is a University of Florida/Institute of Food and Agricultural Sciences commercial horticulture Extension agent for Sumter, Citrus, Hernando, and Pasco counties in Bushnell, FL.