Fumigated shipping containers - venting prior to unpacking by end user

Problem

Shipping containers, fumigated and ventilated by fumigators, may still contain a significant quantity of methyl bromide (MeBr) due to poor venting procedures, desorption or entrapment of the gas in the packaging. This can present a risk to the health and safety of persons involved in unpacking these containers.

Risks

Methyl bromide affects the central nervous system. Depending on the level of exposure, inhalation of MeBr may cause:

• dizziness
• drowsiness
• headache
• nausea
• blurred vision
• numbness
• tremors
• speech defects

Exposure to very high concentrations may cause pulmonary oedema (fluid in the lungs) as MeBr is an irritant. Chronic exposures may also affect other organs.

The national occupational exposure standard for MeBr is 5 parts per million (ppm) averaged over 8 hours.

Controlling risks

The risk to employees who unpack shipping containers which contain high levels of methyl bromide (MeBr) must be eliminated or reduced, as far as reasonably practicable.

The following safety measures should be implemented to control the risks:

• Check if the container has been fumigated. Make reasonable enquiries to check whether the container has been fumigated in Australia or overseas.
• Check for any fumigation warning notice as shown in figure 1.
• Check for a clearance certificate.

If in doubt, treat the shipping container as fumigated.

• Place shipping container in a designated open area with good natural ventilation.
• Set up barricades and warning signs around the entrance to the container to prevent unauthorised access.
• Vent the container by opening the container doors to allow natural ventilation for a short period, or use a blower fan.
  • When opening doors, always ensure to take reasonable care to avoid exposure to any MeBr that may be present.
• Prior to entering the container, vent the container using mechanical ventilation (blowing or extraction) for approximately 30 minutes. This will depend on the nature of the goods and how the container is packed.

Fans or mechanical extraction is recommended if there is:

• highly absorptive material, for example, wood, nuts, seeds or foam rubber
• packaging that may trap the fumigant, for example, boxes or plastic wrapping
• little natural air movement around the container
• tightly packed containers restricting natural airflow

If mechanical ventilation is not practicable or available:

• vent the container using natural ventilation (AS2476-2008 General fumigation procedures recommends 12 hours), or
• prior to entry, test the air within the container using suitable air testing equipment to ensure that the MeBr level is below the exposure standard of 5ppm

If the container is tightly packed, partially unpack it and allow further venting for a short period. Repeat this process until unpacking is complete.

Train relevant employees in safe working procedures for unpacking fumigated shipping containers and in the use of any MeBr testing equipment.

Air testing equipment

If shipping containers are regularly handled, a range of equipment is available to test for MeBr and should be considered.

Air testing equipment varies in user-friendliness and cost, and in detection sensitivity as shown in the following table.

A halogen leak detector (HLD)

A HLD is simple to use, does not require calibration or maintenance. Even with a limitation of detecting MeBr at 15–20ppm, HLD's are useful because they can be used to give an instant warning of the presence of high levels of MeBr, by opening the container doors very slightly and inserting the HLD sampling hose.

When using a HLD, the container needs to be vented according to this procedure as it is not capable of detecting less than 15ppm.

A HLD or any electrical equipment not intrinsically safe must not be used where flammable goods are present.