THE REGIONAL BIOSECURITY
OPERATING PROCEDURES
| STEPS | PROCEDURE FOR SHEET FUMIGATION |
| 1 | Ensure that the concrete or bitumen fumigation slab is clean and free from nails and sharp objects that could damage the fumigation sheet. If the surface is permeable to methyl bromide, then the fumigation must be conducted as an envelope fumigation, with a sheet on the floor beneath the goods. |
| 2 | Assemble the goods or container to be fumigated. Ensure that the goods are all suitable for fumigation. Check the list on page 71. |
| 3 | Put some form of protection over sharp corners. Use used motor tyres, carpets, etc. |
| 4 | Place the gas inlet tube into the stack or container and connect the furthest end of the tube to the methyl bromide source. |
| 5 | Place at least two clear plastic gas monitoring tubes – 9.0 mm outside diameter/ 6 mm internal diameter – into different areas of the container or stack in order to be able to monitor whether gas has adequately circulated to all areas. These tubes must protrude at least three metres from the stack. Seal the ends by bending the tubing and fixing with a large clamp. |
| 6 | Place an electric circulation fan within the stack or container and connect the electric lead to a power point. |
| 7 | Using two or more people, pull a fumigation sheet over the container or stack, roll the corners and seal with large compression clamps to prevent the sheet from flapping in the breeze. |
| 8 | Cover the skirt of the sheet with sand or sand snakes. |
| 9 | Inspect the sheet for holes and tears. Repair with pieces of fumigation sheet and contact glue or use book-binding tape. |
| 10 | Using a measuring tape and calculator, calculate the volume of the fumigation stack or container. |
| 11 | Place a warning sign in front of the fumigation stack. |
| 12 | Complete the fumigation calculation sheet (see Figure 8) by entering details of date, temperature, volume and rate, and calculate the amount of methyl bromide fumigant to be used. If using a set of electronic scales to weigh the methyl bromide, place the cylinder on the scales and record the weight. Subtract the calculated amount and write in the final reading, which must be shown on the scale. |
| 13 | Wearing a respirator, use a halide lamp and check the methyl bromide cylinder, valves and connections for gas leaks. |
| 14 | If the temperature is below 21°C, it is recommended that you fill the vapouriser tank with warm/hot water. |
| 15 | Turn on the circulating fan. |
| 16a | If a decanter is used to measure the methyl bromide, turn on the valve on the methyl bromide cylinder and fill the decanter with the required amount of liquid MeBr (as shown at (c) in the fumigation calculation sheet in Figure 8). Then close the cylinder and open the valve on the decanter to slowly release the gas into the delivery tube, or…. |
| 16b | …..if a set of scales is used, slowly open the valve on the methyl bromide cylinder and allow gas to pass through the vapouriser and into the stack undergoing fumigation until the scale reads the amount of fumigant. |
| 17 | Continue to check for leaks while you feed gas into the stack. |
| 18 | When the calculated amount of gas has been expelled into the stack, turn off the valve. |
| 19 | Turn off the main valve on the methyl bromide cylinder, if it is not already off. |
| 20 | After 20 minutes, turn off the fans and monitor the fumigation using a Riken gas monitor connected to each of the monitoring tubes in turn. If the gas concentration is less than required, check the sheet for leaks, repair any leaks and add additional methyl bromide, if necessary. |
| 21 | Use the Riken to check the gas concentration at various times during the fumigation period. (Refer to Figure 9 for the acceptable concentrations at various intervals after the commencement of fumigation.) |
| When fumigation is finished | |
| 22 | Ensure that there are no people near the fumigation stack. Then, wearing a respirator, remove the sand snakes (or free sand) from the base of the sheet. Remove any clamps on corners and unroll the corners. |
| 23 | Lift the sheet and open at least one end to allow fresh air to circulate and methyl bromide to escape |
| 24 | Turn on the circulation fan and leave the container or fumigation stack to aerate for 30 minutes. |
| 25 | After 30 minutes, turn off the circulation fan and, while wearing a respirator, check for residual gas using a halide lamp. |
| 26 | If the container or stack is free from gas, remove the respirator and remove the fumigation sheet. |
| 27 | Remove the exhaust fan and gas lines before the container or fumigated goods are removed from the fumigation area. |
| 28 | Fold or roll-up the fumigation sheet and store the sheet, monitoring tubes, gas inlet tube, clamps, electric lead and warning sign in a dry place. |
| 29 | Remove any water remaining in the vapouriser and ensure that all valves on the fumigation distribution system are properly turned off. |
| 30 | Ensure that the inside of the respirator is dry, then store it in a clean, dry place. (Where cartridge respirators are used, each date of use and length of time used must be recorded on the cartridge using a permanent marking pen. Cartridges must be replaced at regular intervals.) |
| 31 | Store the Riken gas monitor in a clean dry place. |
An Example of a fumigation calculation sheet (Source: FSM Quarantine Service Fumigation Calculation Book)
| GAS CONCENTRATION
Normal Atmospheric Pressure @ 210C Original Dosage Required minimum concentration (g/m3) (g/m3) Time after commencement of fumigation (Hr) 1/2 1/2-4 4-12 12-24 24-48 32 24 16 11.2 9.6 8 40 30 20 14 12 10 48 36 24 16.8 14.4 12 64 48 32 22.4 19.2 16 72 54 36 25.2 24.6 18 80 60 40 28 24 20 96 72 48 33.6 28.8 24 128 96 64 44.8 38.4 32 |
Table of acceptance concentrations at various intervals after the commencement of fumigation
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