Questions and Answers on Chloropicrin

The pest management industry in the United States relies on fumigation with Vikane gas fumigant to eliminate drywood termites, bed bugs, and other pests that infest and damage residences, businesses, historic sites, and other structures. Vikane is a colorless, odorless, tasteless gas and is non-detectable by people during fumigation. Therefore, as an extra precaution, a very small amount of chloropicrin is released as a warning agent within the structure prior to introducing the fumigant to deter persons from entering and remaining in the structure during the fumigation. For the structural fumigations, chloropicrin is only used in very small doses as a warning agent and not in higher does required for pest control.

In the event that you have questions about the use of chloropicrin in your home or workplace, the following is intended to help answer them.

What is chloropicrin?

Chloropicrin is a colorless liquid with a very strong odor, and it causes eye irritation and tearing when used in small quantities. It is used as a warning agent to deter persons from entering and remaining in the structure during the fumigation.

Why is chloropicrin used?

Vikane is a colorless, odorless, tasteless gas. Therefore, the fumigator will release chloropicrin within the structure at least 5 to 10 minutes prior to introducing Vikane. DowAgroScriences has mandated the use of chloropicrin with fumigation since Vikane was first marketed in 1961 to help safeguard residents, neighbors, employees, and the general public. The use of Chloropicrin is mandated by the Environmental Protection Agency (EPA) as part of the federally approved label for Vikane gas fumigant.

How much chloropicrin is applied?

An extremely small amount of chloropicrin is used as part of the fumigation process. Less than 3 fluid ounces of chloropicrin is released into a typical single-family residence. Chloropicrin is used at a concentration that provides both adequate warning during the fumigation and thoroughly aerates after the fumigation.

What research was conducted to determine the amount of chloropicrin to apply as a warning agent?

Scientists from DowAgroSciences and the University of Florida conducted research from 2000 to 2006 to develop a new calculation system for precisely determining the amount of chloropicrin to apply as a warning agent. Research trials were conducted at 80 residential and commercial buildings in Florida and California. These buildings represented a variety of construction and ranges in size from small (12 thousands cubic feet) to very large (2.7 million cubic feet). Chloropicrin concentrations in structures were measured during fumigation aeration using sensitive analytical equipment. The chloropicrin calculation system based on this research uses fumigation time, structure volume and construction (slab or crawlspace) to prescribe a dose range of chloropicrin specific to the structure to be fumigated. This precision calculation system for chloropicrin is now part of the calculation system (the Fumiguide) for Vikane. This precision calcuation system has reduced the minimum amount of chloropicrin required to apply to medium-large sized structures, such as multi-unit dwellings, by at least 50% compared to previously mandated label application rates while still providing the necessary warning through the time the fumigant is present in the structure.

How is chloropicrin released into a building?

The fumigator carefully measures and pours the chloropicrin onto an absorbent material in one or more shallow pans. The pans are then placed near fans in the area where Vikane will be released. Air movement from the fans helps evaporate the chloropicrin and distribute it throughout the structure. Chloropicrin is released at least 5 to 10 minutes before introducing Vikane to make sure it has sufficient time to distribute prior to release of the fumigant.

Besides using chloropicrin, what other procedures must fumigators follow to deter people from entering the structure during fumigation?

Prior to releasing the chloropicrin, the fumigator conducts a  thorough, room-by-room, walk-through inspection to confirm that everyone, including pets, is out of the structure. The fumigator posts warning signs at all entrances and sides of the structure. In addition, the fumigator locks or barricades doors so that occupants cannot use their keys to enter the structure during the fumigation.

How is chloropicrin aerated from buildings after fumigation?

The California Aeration plan is superior aeration process that has been approved by the California Department of Pesticide Regulation and is approved for all structural fumigations. The procedure requires aeration of the structure with the tarpaulins in place. Strategic placement of fans inside the structure draws fresh air through inlets placed in the tarpaulins and aerates Vikane and the chloropicrin warning agent through ducting. Tarpaulins stay on the fumigated structure for the duration of the aeration process. Following tarp removal, the structure is tested for final clearance and certified for reentry.

Were chloropicrin concentrations measured as part of the development of the California Aeration Plan?

Yes. The California Aeration Plan was developed through extensive research during which chloropicrin was applied at the maximum permitted dose. Chloropicrin concentrations were measured during and after aeration using sophisticated analytical procedures. This research verified that the California Aeration plan effectively aerates chloropicrin.

What should I do if I experience symptoms, such as eye or throat irritation, after the fumigation?

The California Aeration Plan effectively aerates buildings for reentry after fumigation. However, some persons may be able to sense Chloropicrin at extremely low concentrations immediately after aeration. A tiny amount of chloropicrin does not mean Vikane is still present. Vikane aerates from structures more rapidly than chloropicrin, and fumigators use sensitive detection equipment to ensure that Vikane is cleared from buildings prior to allowing re-occupancy.

A few simple steps can assist in clearing any remaining chloropicrin from a building:

If you believe that you sense chloropicrin immediately following the fumigation, leave the building and call the fumigator. A small amount of chloropicrin does not mean Vikane is still present. As a precaution, it is recommended that the fumigator complete the next steps:

  • -Retest to confirm that Vikane has been cleared from the building
  • -Open windows and activate air handling systems
  • -Place additional fans near windows to create a directed air flow for efficient aeration throughout the structure
  • -Increase the temperature within the structure by using only the fan of central air handling/conditioning systems in the warm months and using the central heating system in the cool months.

It may require a few hours for the fumigator to complete these steps. Leave the structure during this time if you continue to experience irritation. Contact the fumigator again for furth assistance if these steps do not remedy the problem.

Is Chloropicrin used for anything else besides a warning agent?

Yes. Chloropicrin is registered with the Environmental Protection Agency (EPA) to fumigate soil to control plant diseases, insects and nematodes prior to planting crops. As a registered pesticide, chloropicrin has undergone significant scientific review for its effects on health, safety and the environment. Chloropicrin is applied at higher rates as a soil fumigant compared to the very small amount used as a warning agent for structural fumigation.

If you have additional questions about chloropicrin or its proper application, contact your professional fumigator.

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