THE REGIONAL BIOSECURITY
OPERATING PROCEDURES
Procedures and use of equipment – Small Chamber Fumigation (as adopted from SPC Micronesia Manual)
Please read and follow these instructions before you start a fumigation.
| STEPS | PROCEDURE FOR SMALL CHAMBER FUMIGATION |
| Preparation | |
| 1 | Before entering the fumigation room where the methyl bromide is stored, light and use a leak detector to ensure that the area is free from gas. |
| 2 | Check all equipment before you start fumigation. |
| 3 | Check the safety equipment. Respirators should be of the full-face piece type, or airline supply. |
| 4 | Check that exhaust/circulating fans are circulating air. |
| 5 | Check the rubber seal on the chamber and ensure the door surface is clean. |
| Fumigation | |
| 6 | Fill the chamber with goods or produce, estimate and record the portion of the chamber that is filled. Ensure that the goods are fit for fumigation – otherwise destroy. |
| 7 | Close the chamber door firmly but DO NOT OVERTIGHTEN. |
| 8 | Measure the ambient temperature. Refer to Table 1 and determine the correct amount of methyl bromide to be used for the required rate at that temperature. Go to Step 9. |
| 9 | Ensure that the exhaust valve is switched to the CLOSED position. |
| 10 | If the temperature is below 21°C, fill the vapouriser tank with hot water.
Make sure that the three valves above the measuring cylinder are closed. |
| 11 | Put on your respirator and light the halide lamp. |
| 12 | Open the valve on the methyl bromide cylinder and then open the right hand valve above the measuring cylinder. Allow the liquid to slowly enter the measuring cylinder until the required volume is reached. |
| 13 | Close the right hand valve. If too much liquid has entered the measuring cylinder, open the centre valve until the liquid level drops to the required reading. Then close the centre valve. |
| 14 | Ensure that the circulating fan is turned on. |
| 15 | Use the halide lamp to check for gas leaks around the methyl bromide measuring cylinder and valves. |
| 16 | Open the left hand valve and allow gas to slowly enter the chamber until the measuring cylinder is empty. Close the left hand valve. Close the valve on the methyl bromide cylinder. |
| 17 | Close the valve on the methyl bromide cylinder. |
| 18 | Use the halide lamp to check for gas leaks around the door seal, at the rear of the chamber and the methyl bromide cylinder. |
| 19 | Record the time. This is the start time for the fumigation. |
| 20 | Place a warning sign in front of the chamber (e.g. Danger! Fumigation in Progress) (Local language). |
| 21 | If a Riken gas monitor is available, measure the gas concentration ten minutes after the start time of the fumigation. |
| 22 | Turn the circulation fan off ten minutes after the start time of fumigation. |
| 23 | If a Riken gas monitor is available, re-measure the gas concentration 20 minutes before the fumigation is timed to end. |
| 24 | Check the time. Make sure you fumigate for the recommended time. |
| When fumigation is finished | |
| 25 | Turn on the circulation fan and use the handle to open the exhaust valve. Wait for about two minutes and then undo the chamber door slightly to allow fresh air into the chamber. Continue to aerate he chamber for 15 minutes or longer. |
| 26 | Turn off the exhaust fan. Light and use a halide lamp to check for gas around the chamber door as you open it completely. |
| 27 | If the halide lamp shows that gas is present in the chamber, close the door, ensure that the exhaust valve is open, turn on the exhaust fan, and continue aerating for a further 15–20 minutes. |
| 28 | Remove the fumigation warning sign. |
| 29 | Open the door and remove the goods. |
| 30 | Complete the documentation. |
To determine the amount of methyl bromide, select the appropriate temperature range from Table 1, then select the rate and read off the amount of liquid to put into the measuring cylinder.
Table 1: Methyl bromide fumigant dosage rates for small 1.1 m3 chamber
| Temperature Range | Required rate (g/m3) | Dosage (ml/cc) |
| 17°C–25°C | 32 | 21.0 |
| 40 | 26.0 | |
| 48 | 31.0 | |
| 80 | 52.0 | |
| 128 | 83.0 | |
| 26°C and above | 32 | 15.5 |
| (a correction of –8 g/m3 has been made for each temperature increase of 5°C) | 40 | 21.0 |
| 48 | 26.0 | |
| 80 | 46.5 | |
| 128 | 77.5 |
Example of chamber operation
The volume of many small chambers in the Pacific region that have been provided by Australian aid projects is 1.1 m3 and the methyl bromide is measured by volume, not weight. Methyl bromide has a specific gravity (sg) of 1.7 and is therefore heavier than water (sg 1.0).
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