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Department of Pesticide Regulation MEMORANDUM HSM-10008: RECOMMENDATIONS FOR A REAL-TIME AIR MONITORING SYSTEM

  • By : PureAire Monitoring Systems
  • Posted on : July 14, 2012

On June 16th 2010, I traveled to Los Angeles County to conduct a third workplace evaluation of a proposed enclosed fumigation site (see Health and Safety Memorandum [HSM] 09008) and to specify sampling protocols for real-time monitoring of intermodal fumigations at a Long Beach facility. Previous visits to this facility were at the request of the Los Angeles County Agricultural Commissioner’s (CACs) Office. CAC staff was present during both consultations. Additionally, the manager of the facility and the fumigator contracted for the applications were present.

The purpose of this visit was to evaluate a newly constructed enclosure in Building 4, a building that was involved in buffer zone conflicts with an intermodal fumigation site located in the adjoining parking area. The fumigator had proposed to fumigate intermodal vans close enough to Building 4 that the buffer zone would potentially extend into the enclosed work area. Additionally, the site manager was proposing abandonment of both a fumigation site in Building 3 and an intermodal fumigation site located between Buildings 3 and 4. In essence, they were proposing to conduct the bulk of their fumigations in or near Building 4.
The “near” site is a location where they plan to fumigate intermodal trailer at a parking lot adjoining Building Four. This location was such that buffer zones would still intrude into structures where workers would be present. This results in non-compliance with the “Suggested Permit Conditions: Methyl Bromide Commodity Fumigation” (MBr Permit Conditions) concerning Definition R/Condition 19: Treatment Zone Access and Duration.

The “in” site is a newly constructed structure within Building 4. It is defined by the exterior north and east walls of Building 4 and two interior walls orthogonal to the exterior walls, forming a cubic containment structure. This area will be used to fumigate pallets of produce. Once again, the location was such that buffer zones would intrude into enclosed structures where workers would be present. This results in non-compliance with the “Suggested Permit Conditions: Methyl Bromide Commodity Fumigation” (MBr Permit Conditions) concerning Definition R/Condition 19: Treatment Zone Access and Duration.

In an effort to address the non-compliance, the facility manager had obtained a PureAire methyl bromide (PAMB) monitor, capable of real-time monitoring of fumigant air concentrations. The manufacturer of this monitor has stated that they can achieve detection limits of 500 parts per billion (ppb).

Normally, such a unit would be installed in a central location and remote detectors strategically located. However, the facility manager has set the detector and processor/readout on a portable platform (Photo ONE) and will move the unit through a predetermined route during the fumigation/aeration process.This route includes five sampling stations I identified as necessary to evaluate potential methyl bromide exposure to persons working on this loading dock in Building Four. These stations form a perimeter around the fumigation enclosure and should intercept and detect leakage from the enclosure. They were also selected as being the most likely leakage spots (structural material discontinuity, structural access penetrations). By deploying the PureAire methyl bromide -monitoring system, and following all the requirements described below, Building Four may be occupied while tarped-stack (pile) fumigation/aeration in the interior enclosure is performed.The sampling stations for inside fumigations are as follows:

Station One: East side wall, by egress door (door to be modified, by signage or other suitable method, to preclude opening during active fumigation, except in an emergency; door must not be rendered inoperable for emergency exit)

Station Two: By metal support beam running vertically along enclosure wall, approximately midway between east side wall (Station One) and end corner of wall (Station Three).

Station Three: At corner intersection of two interior walls.

Station Four: By metal support beam running vertically along enclosure wall, approximately midway between south side wall (Station Five) and end corner of wall (Station Three).

Station Five: By rollup door of interior wall, next to southern exterior wall.
These stations shall be marked on the floor. The PureAire methyl bromide will spend a minimum of 5 minutes, up to a maximum of 10 minutes at each station. Monitoring will continue during the fumigation phase, cycling through the stations (1-2-3-4-5-4-3-2-1) until the active fumigation is completed and the aeration buffer zones have collapsed. Additionally, a 10 foot buffer around the interior wall shall be painted on the floor adjacent to the interior walls and no items may be stored in this area during active fumigation. No workers, other than the PureAire methyl bromide operator/tender, may work in this zone. Only momentary transit through this zone is allowed for all other workers.

Furthermore, given the volume of this structure, additional conditions are necessary to mitigate potential buffer zone and fugitive emission problems:

1. Seal airtight all penetrations on both sides of the primary fumigation enclosure, including power outlets, breaker boxes, switch boxes, door gaps, etc.

2. Only tarped tarped-stack fumigations are allowed. This is not a fumigation chamber. All requirements of Title 3 California Code of Regulations Section 6782 apply.

3. An exhaust stack of sufficient height, as calculated by DPR’s Environmental Monitoring Branch, shall be installed on the roof. Do not situate this stack such that any interior-directed roof fan recaptures the exhaust air and sends it back into the general air space.

4. All persons entering the primary fumigation enclosure area during fumigation or aeration must wear SCBA. Entrance during fumigation or aeration shall only be from an exterior wall door (not from interior wall doors).

5. If during the retrofitting to fully seal the primary fumigation enclosure and provide for a sufficiently high exhaust stack conditions not mentioned in this list are found that can affect the seal integrity of the structure, the Department of Pesticide Regulation/Worker Health and Safety Branch/Industrial Hygiene and the LA CAC must be notified both of the condition and the proposed solution.

6. Any fumigation monitoring equipment must exhaust back into the fumigation area.

7. Necessary security and warning requirements will be installed.

8. In using the real-time PureAire methyl bromide -monitor for interior fumigations, a history of monitoring may be established. If after 25 separate and distinct fumigation events no detectable concentrations over 0.7 ppm are recorded, monitoring of every fumigation may be discontinued. This is allowed in the MBr Permit Conditions under Condition Four: Enclosed Areas/Common Walls: Test Procedure for Enclosed Areas. After compilation of the 25 fumigations, only every fifth fumigation need be monitored. However, no fumigation rates in excess of the maximum rate used during the monitoring period may be used, nor may there be any structural changes to the primary fumigation enclosure (intentional or accidental) or changes to the main structure that would decrease the openings to the exterior as presently configured. If there are, another monitoring of 25 events must be conducted.

9. The 25 fumigation historical data is only good for one year. One year after the completion of the last of the 25 fumigations, another compilation of 25 fumigations must be performed. Also, any detection of methyl bromide of 0.8 ppm or greater will reset the data compilation requirements (this includes during the every 5th fumigation monitoring).

10. All otherwise applicable requirements of the MBr Permit Conditions still apply.

11. The data logging requirements of “Outdoor Intermodal Fumigations” are also in effect (see below).

As for fumigation of intermodals or other exterior stack fumigations, the general requirements of HSM-09008 will be in effect (but only if no interior fumigation is in process or will be commenced during any exterior fumigation/aeration cycle):
OPTION TWO FOR BUILDING FOUR/Outdoor Intermodal Fumigations: If a real-time air monitoring system, specific for methyl bromide, is installed in Building Four, only the two rollup doors closest to the fumigation and aeration need be latched and locked. Deployment of the detector’s sensors should be such that they are not unduly affected by outside air (i.e. not right next to openings to the exterior) and that they are located in areas that an intruding buffer zone would be located. This monitoring system will need to be maintained and calibrated according to the manufacturer’s recommendations and be capable of data logging, recording at a minimum of 5 minute intervals during fumigation and aeration events. When there are no fumigations or aerations, logging may be suspended. The data logs must be available for CAC inspection and a hard copy maintained for 3 years. Exit doors that are immediately adjacent to the latched and locked rollups should be equipped with emergency alarms and designated “EMERGENCY EXIT ONLY” during the fumigation and aeration buffer zones. Do not chain off or otherwise render inoperable any exit door.

The company also plans to use the PureAire methyl bromide to monitor the outdoor intermodal fumigations. Four sampling stations were identified. These were selected to be sufficiently distant from the open rollup doors to not be affected by outside air movement, yet still allow early detection of intruding methyl bromide leaks. The sampling stations for outdoor intermodal fumigations are as follows:

Station Ten: Between rolled down loading dock doors, adjacent to the interior fumigation structure.

Station Twenty: At metal support pole previously agreed upon.

Station Thirty: At metal support pole previously agreed upon.

Station Forty: By office fence.

These stations shall be marked on the floor or on the appropriate support pole. The PAMB will spend a minimum of 5 minutes, up to a maximum of 15 minutes at each station. These conditions apply for outdoor intermodal fumigations only; no interior fumigation can be in process or will be commenced during any exterior fumigation/aeration cycle.
Under conditions where both outdoor intermodal and indoor stack fumigations will be performed simultaneously or where the initiation of fumigation of one site will be conducted during any part of the fumigation/aeration cycle of the other, the following additional requirements must be met:

1.All stations (1-5 and 10-40) must be sequentially monitored for at least 1 minute and no more than 5 minutes per station. Monitoring will continue during the fumigation phase, cycling through the stations until the active fumigation is completed and the aeration buffer zones have collapsed.

2.Two closest rollup doors to the interior structure shall be closed.

3.All other conditions of “interior only” applications will be followed.
Under all situations, monitoring will begin when the fumigant it first injected, and shall cease when the initial aeration period, normally requiring buffer zones, is completed, or when label aeration requirements are met, whichever is longer. A general sampling protocol (how long at each station, who is responsible for the system, when will it be deployed, what physical conditions the dock should be in, etc.), based on the recommendation of this memorandum, must also be developed. These protocols must also define actions to be taken when a trigger value is detected and the affected workers must be trained as to their actions if such an event occurs. Recommended trigger value actions are:

– 0.5 ppm methyl bromide detection: no restrictions
– 0.5 to <0.7 ppm methyl bromide detection: restricted work period of up to 8 hours for all workers within Building 4. - 0.7 to <0.8 ppm methyl bromide detection: restricted work period of up to 6 hours for all workers within Building 4. - 0.8 to <1.2 ppm methyl bromide detection: restricted work period of up to 4 hours for all workers in Building 4. Investigate exposure source, remediate before next fumigation. - 1.2 ppm to <2.4 ppm: If trigger values are detected twice within a 30 minute period, evacuation of all non-fumigation personnel from Building 4 and begin immediate aeration procedures on all indoor fumigations. Investigate exposure source, remediate before next fumigation. Test air before allowing workers to reenter, concentrations must be <0.7 ppm.  >2.4 ppm: Immediate evacuation of all non-fumigation personnel from Building 4 and begin immediate aeration procedures on all indoor fumigations. Investigate exposure source, remediate before next fumigation. Test air before allowing workers to reenter, concentrations must be <0.7 ppm. This protocol should be reviewed by the CAC as to its feasibility, comprehensiveness and correlation with Title 3 California Code of Regulations Section 6780: General Fumigation Safe-Use Requirements. The above listed recommended trigger actions should be formatted into a poster and posted in the affected workplace as part of the employee training for response to a methyl bromide exposure incident. cc: Richard Sokulsky, Los Angeles CAC Office Aniko Pomjanek, Los Angeles CAC Office Peggy Byerly, Environmental Scientist, Enforcement, Southern Regional Office (SRO), DPR Jahan Motakef, Environmental Program Manager I, Enforcement, SRO, DPR Susan Edmiston, Environmental Program Manager II, Worker Health & Safety Branch, DPR