Preventing Indoor Pesticide Drift

Drift is the uncontrolled airborne movement of pesticide spray droplets, vapors, or dust particles away from the intended point of application. While drift is most frequently associated with outdoor applications, it may also occur indoors via air currents created by ventilation systems, forced-air heating or cooling systems.

Drift may result in injury to humans, nontarget plants and animals; potential illegal residues on nontarget sites; and a waste of product.

All pesticides can and will drift if not applied properly, thus making drift an important environmental and health concern.

Although pesticide drift cannot be completely eliminated with today's technology, drift can be reduced significantly and managed to avoid potential problems. Under federal and state regulations, all pesticide applications must be performed in such a manner as to prevent off target movement from the intended application site.

Certain pesticide formulations also have a potential to vaporize (are volatile) and move off target. This is a result of the pesticide formulation having a high vapor pressure. The chance for a pesticide to move off-target as the result of volatilization increases as the air and surface temperatures increase, relative humidity decreases, particle or droplet sizes decrease, and air movement increases.

Drift control is every applicator's responsibility. In fact, many labels specify that off-target movement is the responsibility of the applicator. Drift control frequently involves a series of trade-offs. Each application may involve a different approach to minimize the drift problem.

The following tips are some best management practices that can be used to help minimize the potential of drift or volatilization from occurring.

Avoiding drift with spray & dust applications

Turn off fans, air conditioners, forced-air heat, furnaces and other air circulating equipment that could cause the insecticide to enter an air intake duct and be moved to other areas of the structure.
To reduce the potential for drift, use low volatility or nonvolatile insecticides, such as baits, pastes and gels.
Low pressure, crack and crevice, and void injections should be used since they will further minimize the potential for indoor drift.
In order to obtain the best results with a compressed air sprayer, use a low pressure to prevent splashing and splattering. The use of high pressure causes the sprayed liquid to break into fine droplets which will more readily move from the target area.
When treating wall voids with dust, use application equipment that gives the dust particles an electrostatic charge so they stick to surfaces inside the void. To give dust an electrostatic charge add a couple of marbles or ball bearings to the duster.
Never use dusts in suspended ceilings or where drafts could blow dusts into non-target areas.
When treating voids with a power duster, use a low pressure to reduce the chances of drift. This also holds true for the use of bulb or bellow type dusters.
Never spray pesticides into ceiling voids that are above food preparation or living areas.
When using dusts, apply them as a thin film. Heavy dust applications actually repel pests and increase the potential for the dust to be carried to nontarget areas.

Avoiding drift with termiticide applications

Pay particular attention to sub-slab duct work. Thoroughly inspect the structure and document the location, depth and width of the duct work. Also inspect the duct work with a mirror to determine if there are any breaks in the system.
In crawl spaces, pay attention to air intakes and inspect for faulty duct work. The air from the crawl space may be circulated into other areas of the structure by the heating and air conditioning system. This will result in the movement of vapors or odors throughout the structure.
Make sure that the furnace and/or air conditioner is turned off prior to treating a crawl space. Also make sure any air intakes located in the crawl space are closed.Remember, the new termiticide labels require the air circulation system of the structure to be turned off until the application has been completed and all termiticide has been absorbed by the soil when treating crawl spaces.
Vapors resulting from a termiticide application can be reduced by the use of fans to ventilate the crawl space during application and until the pesticide dries. Placing a vapor barrier over treated soil can also help to reduce vapors.
Never apply a termiticide in a crawl space that has saturated soil. The termiticide will not bind with the soil, resulting in it remaining as an emulsion that can produce vapors for an extended period of time.

Drift control is the applicator's responsibility

Remember that drift control is every applicator's responsibility.

The goal of proper application of pesticides is to achieve uniform distribution while retaining the pesticide within the intended application site. This can be accomplished by using the proper equipment and application techniques.

Remember to always read the label, follow all application precautions and restrictions, and utilize best management practices to prevent the off-target movement of pesticides.