For larger enclosures it is advisable to use a higher capacity fan and, for large stacks over 100 m³, multiple fans would further assist in achieving equilibrium. Turn the fan/s on 5 minutes to 10 minutes prior to injecting the gas to get the air moving. As the methyl bromide is injected this will encourage the methyl bromide to mix with the air and be distributed throughout the enclosure. Even though methyl bromide is heavier than air the tendency for it to accumulate in higher concentrations lower down in the enclosure is minimal during normal fumigation exposure periods if it has been thoroughly mixed with the air from the beginning. The fans must be running during the injection phase and for as long as necessary to achieve equilibrium. The fans should be turned off prior to taking the concentration readings to allow the air in the enclosure to settle. This helps to get more accurate and stable readings. It is not necessary to run the fans again once equilibrium is achieved unless additional methyl bromide is added to the enclosure. Monitoring fumigant concentration levels The principal objective of fumigation is to maintain an adequate concentration of fumigant within the enclosure for a sufficient length of time for all pests, including different stages of their life cycle, to receive a lethal dose. The only way to determine if the minimum concentration levels have been met is to take concentration readings at the start of the fumigation and again at the end. If both these readings are at or above the minimum level specified for the time they were taken, then the concentrations have met the minimum requirements throughout the entire exposure period. Every concentration reading must also show the time at which it was taken. When taking readings from more than one sampling tube, the time should be recorded after the final concentration reading was taken, and used as the time for all the readings in that set. Concentration measuring instruments There are a number of suitable monitoring instruments that can be used. While price is always a significant factor in choosing equipment, careful consideration should be given to the reliability and ease of use. Some of the brands on offer can be more difficult to use in the field then it would first appear. It would be prudent to carefully research what brand and model would represent the best choice to suit each fumigator’s individual circumstances. When deciding on a fumigation monitoring instrument you should consider the following: accuracy detection range durability reliability
For larger enclosures it is advisable to use a higher capacity fan and, for large stacks over 100 m³, multiple fans would further assist in achieving equilibrium. Turn the fan/s on 5 minutes to 10 minutes prior to injecting the gas to get the air moving. As the methyl bromide is injected this will encourage the methyl bromide to mix with the air and be distributed throughout the enclosure. Even though methyl bromide is heavier than air the tendency for it to accumulate in higher concentrations lower down in the enclosure is minimal during normal fumigation exposure periods if it has been thoroughly mixed with the air from the beginning. The fans must be running during the injection phase and for as long as necessary to achieve equilibrium. The fans should be turned off prior to taking the concentration readings to allow the air in the enclosure to settle. This helps to get more accurate and stable readings. It is not necessary to run the fans again once equilibrium is achieved unless additional methyl bromide is added to the enclosure. Monitoring fumigant concentration levels The principal objective of fumigation is to maintain an adequate concentration of fumigant within the enclosure for a sufficient length of time for all pests, including different stages of their life cycle, to receive a lethal dose. The only way to determine if the minimum concentration levels have been met is to take concentration readings at the start of the fumigation and again at the end. If both these readings are at or above the minimum level specified for the time they were taken, then the concentrations have met the minimum requirements throughout the entire exposure period. Every concentration reading must also show the time at which it was taken. When taking readings from more than one sampling tube, the time should be recorded after the final concentration reading was taken, and used as the time for all the readings in that set. Concentration measuring instruments There are a number of suitable monitoring instruments that can be used. While price is always a significant factor in choosing equipment, careful consideration should be given to the reliability and ease of use. Some of the brands on offer can be more difficult to use in the field then it would first appear. It would be prudent to carefully research what brand and model would represent the best choice to suit each fumigator’s individual circumstances. When deciding on a fumigation monitoring instrument you should consider the following: accuracy detection range durability reliability
guide-qps-fumigations-methyl-bromide.docx