Thursday, April 4, 2013

FUMIGATION vs. LOCAL TREATMENT



A fumigation is the process of tenting and saturating an item (mattress, furniture, food, etc.) or structure (building, boat, railroad car, truck, silo, etc.) with a fumigant, commonly called a gas, to eradicate infestations.

In some instances infestations (drywood termites, beetles, bed bugs, etc) can be so widespread or extend into inaccessible areas that a local treatment is no longer feasible or even possible.  Since year 2000 Sufuryl fluoride has been used to replace methyl bromide. Sufuryl Fluoride is a true gas, not a mist, vapor, powder or suspension. The gas is used to replace the oxygen in the item or structure and asphyxiate the target insects.

Larkspur City Hall & Fire Department
Each year thousands of small and large fumigations occur; mattresses with bed bugs, furniture with beetles, shipping containers, railroad cars and trucks transporting food with pests, and large structures infested with drywood termites, beetles or bed bugs such as multi-unit apartment buildings, university dorms, barns and silos, warehouses, shopping centers and even public buildings like churches, schools, libraries, airports, and museums - only to name a few.

Sufuryl fluoride (SO2F2) is an inert fumigant gas commonly used because it easily penetrates wood members to reach into inaccessible areas where insects live and feed. When fumigating the structure, the treatment reaches into every areas and wood members of the structure (attics, walls and floors) killing all target insects.

Pros and Cons of Fumigation
The biggest pro of a fumigation is that it is a sure kill to all areas and since this is a true gas that is lighter than air, there is no residual effect on the fumigated structure or its content. The fact that there is no residual effect is a great advantage, whether it is crops or structures, but it is also its greatest short coming as once the fumigation is completed, there is nothing keeping pests from re-infesting the structure or its contents.

But fumigation has cons too: It is a costly process that requires vacating the structure for several days. The length of the fumigation will vary depending on the insect to be eradicated:  1 to 2 days for bed bugs, 3 days for drywood termites and 5 days for beetles. The cost and dose of the fumigant used will also vary with different insect infestations: 1 dose for drywood termites, 3 doses for bed bugs, 10 doses for beetles. Fumigation is more costly and inconvenient than local treatments, as the structure to be fumigated will require preparation.

The Process
Single Family Home in Point Reyes
Prior to fumigation, owners and occupants must do some preparation to the structure: Removing pets, plants, medicine, food and opened containers, as well as trimming plants and disconnecting attached fences, arbors and the gas meter. Since the fumigation will lessen the oxygen content in the structure, the pilot lights must be extinguished before and re-lit after the fumigation. The fumigant is lighter than air, so before injecting the fumigant, the structure is completely sealed with tarps (tenting), which contains the fumigant in the building so it penetrates wood members and kills the insects (termites, beetles, bedbugs, etc.). Once the fumigant is injected, the building remains sealed for 12 to 72 hours depending the infestation, building, location and job complexity. Large visible warning signs are posted around the building to notify people to keep out.

On the last day before removing the tarps, the structure is aerated by opening vent traps in the tarps. Fans are used to clear the building of the fumigant and restore the natural air environment. Once thoroughly aerated, a state licensed fumigator measures the level of any remaining fumigant to ensure it meets the strict EPA requirements before re-entry.  The gas will not be reconnected until the building is cleared for re-occupancy by a state licensed fumigator.

Are there any alternatives?
Other attempts have been made in the past to find alternatives to fumigation. Among them are: Heat, freezing, microwave and non-pesticide injections. All these options have advantages, limitations and drawbacks.

Heating: Lab test have shown that high heat does kill termites effectively. A heat treatment consists in bringing the core of infested wood members in a home or wall to 120 to 130 degrees Fahrenheit (45-50 Celsius) for at least 35 minutes to an hour. The home is tented and heated until all wood members achieve the desired temperature. The treatment is very effective in a controlled environment but heat can cause damage to many components (plastics wiring, ABS drain lines, PVC pipes, vinyl windows, roof shingles, etc.) commonly found in structures and to heat sensitive furniture and belongings. Additionally, with today’s increasing price of energy, the associated cost has become less attractive than other treatments and this method is now seldom used except in a controlled environment like kiln dried lumber or crops that can be heated.

Freezing: A Freezing treatment consists in lowering the temperature in the core of the infested wood members to below freezing to kill termites. Sometimes used locally, it is not practical for entire structures as too many components can be damaged by the cold (plumbing pipes, windows, skylights, electronics, lighting, occupant belonging, etc.). Quite successful in test labs but impractical and costly in the real world, it is no longer used except in very controlled environments for smaller items.

Microwaving: Microwave treatment consists in mounting microwave generators on one side of a wall and a protective shield on the other side, then bombarding the wood members for a specific period of time. This has to be done one stud at a time and is limited to areas without metal parts such electrical wiring, plumbing, ducting, etc.). Though efficient in controlled lab environments, it is ineffective in areas that are inaccessible and is nowadays seldom used and not cost effective compared to local chemical treatments.

Bio-Control: Bio-Control or “non-toxic” local treatments have also been attempted using nematodes (microscopic worms) injected into galleries to kill termites. But results were disappointing and this bio-controlled treatment is no longer used.

Local Termiticide Treatment/Injection
Citrus or Orange Oils: Attempts have been made with citrus terpene such as orange oil. But results are disappointing, less reliable and orange oil treatments are often used in conjunction with other longer lasting termiticide treatments. Marin Termite Control has used orange oil in the past but treatments are less effective than other termiticides like TimBor, BoraCare and Termidor. Orange oil has become more a marketing gimmick than a dependable solution to eradicate termites and wood boring beetles (see our blog on orange oil treatments).

Borate Based Insecticides:Borate based inorganic material has proven successful; however this is type of treatment is only effective on small localized infestations. Marin Termite Control has used borates such as TimBor (disodium octaborate tetrahydrate) and still uses it against wood boring beetle infestations. However, since its interior approval in 2005, we have observed a greater success rate with the use of Termidor termiticide injections for local treatments against Drywood termites. 
Why Sufuryl Fluoride, and not Methyl Bromide?
Methyl Bromide (MeBr) is an odorless colorless gas that has been used extensively in the past as a fumigant against pest infestation. However, past studies and scientists have shown that methyl bromide contributes to the depletion of the ozone layer and the product has been phased out in the US and many other countries since 2000. It has also been observed that Sufuryl Fluoride penetrates and dissipates through wall coverings and wood members better than methyl bromide, leaving the fumigated structure with even less fumigant than methyl bromide.

How do we know when it is safe to return?
Tenting Before Fumigation
The state licensed fumigator will check every room, closet and space for any remaining gas in the structure. Once cleared, the licensed fumigator will post a notice of Re-Occupancy at the front of your building indicating the day and time for safe re-entry. Structures can only be re-occupied when concentration of fumigant is less than 1 part per million, this includes a considerable safety margin. Tests have shown that exposure to 100 parts per million presented no adverse affects on subjects. Fumigants are a true gas, not a vapor, leave no residue and aeration is rapid. Studies show that, in most structures, less than 1 part per million remain after tarp removal and no detectable levels of fumigant within 24 hours after aeration.

What are the problems associated with fumigation?
Fumigations are more costly and inconvenient than localized treatments. The item or structure to be fumigated must be vacated for several days depending on the infestation. It is also more labor and material intensive and has a higher cost of treatment. However, fumigations are all encompassing treatment and come with a warranty against re-infestation depending on the insect. When the whole structure is treated, all target insects are killed, even the undetected and unreachable ones. This is particularly critical if more than one colony has infested the structure.

Fumigation is hard on the house and adjacent landscape. No doubt about it. Unfortunately, as careful as fumigators try to be, workmen walking around and tarping a structure may take a toll on plants, landscaping and roof shingles. We use reputable fumigators that are thoroughly trained and experienced to keep disturbance and interference to an absolute minimum. The vast majority of homes we fumigate, experience no damage.   

What about other residue & side effects?
Tented Multi-Unit Condominium
Understandably most people are weary when a gas is used in their home. Sufuryl fluoride, used since 1961, is non-flammable, non-corrosive, odorless and leaves no residue. Sufuryl fluoride is lighter than air, and after your house is thoroughly vented and tested by a state certified professional, the little fumigant that may remain in wall voids and attics will dissipate up into the atmosphere just as quickly as it penetrated the structure to eliminate drywood termites. Over a million buildings have been fumigated with Sufuryl fluoride. Many homes are fumigated each month with no problems. All precautions are taken to ensure not only your safety, but also ours and that of our inspectors and experienced crew members.

What preparations should be done to the house?
When a fumigation schedule is requested and a date is set, Marin Termite and the fumigation crew will provide you with printed instructions including a preparation checklist including a list of items to remove from the structure before the set fumigation date. Additionally, we remain available to answer questions via phone (415-456-9620)