Pre-Fumigation Preparation: Inspection, Notification, and Structure Sealing

Why Pre-Fumigation Preparation Matters

Structural fumigation uses penetrating gas fumigants—most commonly sulfuryl fluoride—to eliminate wood-destroying insects and other pests throughout an entire building. Because these gases are invisible, odorless in their pure form, and highly toxic, every mistake made before the tarp goes down can become a life-safety emergency. Pre-fumigation preparation is the phase where you eliminate those mistakes. It is not paperwork for its own sake: it is the professional and legal foundation on which every safe, effective fumigation job rests.

State pesticide law and the fumigant label (which is a legal document under FIFRA) both impose specific pre-fumigation duties. Failing to follow them can result in license revocation, criminal liability, and—most seriously—injury or death to occupants, neighbors, or your crew.

The Pre-Fumigation Inspection Walk-Through

Before any fumigant is released, the lead technician must walk every accessible area of the structure with a checklist. The goals of the walk-through are:

• Confirm the structure is clear of all occupants, including people, pets, and plants. No exceptions. Birds, fish in tanks, and houseplants are all killed by fumigants at label rates.
• Locate and document all utility shutoff points. Natural gas must be shut off at the meter before fumigation begins because fumigants can be carried through gas lines or be ignited under certain conditions; the gas company is typically notified and may require their own technician. Electricity to appliances with pilot lights should be addressed per label and local requirements.
• Identify every point of egress. All doors, windows, vents, and roof hatches must be accounted for so they can be sealed and later verified before re-entry.
• Check for connected structures. Attached garages, shared walls with neighboring units, or utility tunnels can allow gas to migrate. These must be disclosed and addressed before fumigation.
• Note any structural conditions (gaps in the roof deck, broken vents, deteriorated eaves) that will affect how well the tarpaulin seals and how quickly gas concentrations build and disperse.

Complete your checklist in writing during the walk-through. A checklist completed from memory after the fact is not a reliable safety tool.

Occupant Notification Requirements

State regulations and the fumigant label require that occupants receive notification before they vacate. Notification is not optional and not casual. You must:

1. Deliver written materials that include the fumigant name, active ingredient, the warning sign that will be posted, and the estimated re-entry date and time.

2. Verbally explain what items must be removed or bagged, where occupants can stay, and how they will be contacted when the structure is cleared for re-entry.

3. Post EPA-required warning signs at all entry points before fumigation begins. These signs must remain posted until a certified applicator has confirmed the structure is safe and cleared the signs.

4. Document the notification on the fumigation order form with the date, time, and signature or acknowledgment of the occupant or their representative.

Be prepared to answer occupant questions clearly and accurately. Common questions concern the safety of food left inside, what happens to houseplants, and when they can return. Your answers must match label language and your company's procedures.

Food, Drug, and Sensitive Item Preparation

Fumigant gases penetrate most common packaging materials. Items that are not in their original airtight, sealed containers must be removed from the structure or placed in gas-impermeable bags before fumigation.

Gas-impermeable bags (often referred to by the trade name Nylofume, though equivalent products exist) are the industry standard. These bags are made from a multilayer film that fumigant gas cannot penetrate at the concentrations and exposure times used in structural fumigation. Proper use requires:

• Placing items loosely enough that the bag can be sealed completely.
• Folding and securing the open end with the twist-ties provided, making a tight, multi-fold seal. A loose twist-tie wrap is a common error that defeats the purpose of the bag.
• Not overfilling bags—an overfull bag cannot be sealed correctly.

Items that must be bagged or removed typically include: any food or feed not in original unopened airtight metal or glass containers, medicines and vitamins, tobacco products, and items specified on the label. Check the current label for the fumigant being used, because requirements can differ between products.

Items that must be removed entirely include living things (people, pets, houseplants, fish) and items the label specifically prohibits bagging.

Tarpaulin Inspection

The tarpaulin (tarp) traps fumigant gas inside the structure. A compromised tarp is both an efficacy failure and a safety hazard to neighbors and passers-by. Before use, inspect tarps for:

• Tears, punctures, or thin spots. Even small holes allow gas to escape.
• Worn or damaged tape strips and clamps along the edges used for ground sealing.
• Correct size. The tarp must extend to ground level on all sides and be properly sealed to prevent gas escape at the foundation.

Damaged tarps must be repaired with compatible patching tape or taken out of service. Never assume a tarp that "worked last time" is still serviceable without inspection.

Personal Protective Equipment and Safety Reminders

During pre-fumigation preparation you are not yet exposed to fumigant, but you must have the correct PPE staged and ready before gas introduction begins. Self-contained breathing apparatus (SCBA) or supplied-air respirators required for gas introduction must be inspected and fit-tested. Review your company's emergency action plan and know the location of the nearest exit at all times. Never enter a tented structure after gas introduction without appropriate respiratory protection and a cleared gas reading.

Completing the Checklist

Every item on the pre-fumigation checklist is there because a real incident revealed the need for it. Treat every line as mandatory. State regulations and the label set the minimum standard; your checklist must meet or exceed that standard. All 12 mandatory items must be addressed before fumigation proceeds. Safety-critical items—occupant clearance, gas shutoff, warning sign posting—allow no partial credit.