Which statement is true regarding fumigation sealing, particularly with phosphine?

• A. Sealing is essential for fumigation effectiveness.
• B. Venting to atmosphere is encouraged.
• C. Ignoring soil moisture is acceptable.
• D. Quick shallow application is sufficient.

Answer: (A)

Maintaining a tight seal around the treatment area is essential for phosphine fumigation to work. The gas has to stay inside long enough and reach every space pests may inhabit, including cracks, voids, and soil pores, which a leak would prevent. A sealed space preserves the gas concentration and reduces the risk of exposure to people outside the treated area, while also ensuring the fumigation is effective across the entire treatment zone. Ignoring soil moisture or applying the product only shallowly undermines how the gas distributes through the soil and structures, so both moisture management and proper application depth are important. Venting to the atmosphere during the exposure period would quickly dilute the gas and diminish pest kill, so it’s not encouraged.