Fumigated shipping containers — clearance of methyl bromide by fumigators

Fumigated and ventilated shipping containers can contain high levels of toxic methyl bromide (MeBr). This guidance is for employers and outlines safety measures to reduce MeBR levels in containers.

Problem

Shipping containers that are fumigated and ventilated may still contain high levels of MeBr due to poor venting procedures, desorption or entrapment of the gas in packaging. This can present a risk to the health and safety of the persons involved in unpacking these containers.

Risks

MeBr 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 various other organs.

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

Controlling risks

This document provides health and safety guidance for employers on how to control the risks associated with MeBR levels in fumigated shipping containers. This document does not provide guidance on how to fumigate the container safely.

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. This can be achieved by the following safety measures:

  1. Prepare the container before introducing the fumigant by:
    • ensuring sufficient space between packages for air circulation to make it easier to vent the container (for example, repack on pallets)
    • unpacking the container and fumigating it as a less than container load (LCL)
    • making holes in packaging or shrink wrapping to prevent fumigant being trapped.
  2. Set up mechanical ventilation within the container to circulate the MeBr during fumigation and to vent the container on completion of fumigation.
  3. Set up sampling tubes within the container (at least 1.5–2.0 metres from the door) to monitor the level of MeBr, during fumigation and when clearing the container.
  4. Fumigate the container as required by the Australian Quarantine and Inspection Service (AQIS).
  5. On completion of fumigation, ventilate the container using natural and/or mechanical ventilation (blowing or extraction) until the level of MeBr is less than 5ppm.

Ventilation

Mechanical ventilation is recommended where the container is tightly packed, highly absorptive material is present or there is packaging that may trap the fumigant.

Various types of mechanical ventilation are shown in figures 2, 3 and 4.

  1. Prior to testing for MeBr, turn off any mechanical ventilation and allow the container to sit for at least 30 minutes to allow for any desorption or diffusion through packaging.
  2. Test for MeBr within the container using suitable equipment capable of detecting less than 5ppm.
  3. If levels of MeBr greater than 5ppm are detected, repeat the ventilation process until a level less than 5ppm is achieved.
  4. Provide information to warn the transport company and end-user that the container has been fumigated with MeBr, ventilated and precautions to be taken by:
    • placing a fumigation warning notice across container doors (a suitable warning notice as per AS 2476-2008 General fumigation procedures is shown in Figure1)
    • issuing a clearance certificate to indicate the date of ventilation, time and safe level of MeBr achieved (less than 5ppm).
Warning label - Contents have been fumigated with (name of fumigant) and ventilated. Residual fumigant may be present. Ventilate or test before entry.

Figure 1: Warning notice across container doors should be at least 14cm x 10cm external dimensions.

Illustration of an industrial electric fan for use in mechanical ventilation.

Figure 2: A heavy-duty portable fan.

Illustration of a purging fan with flexible duct for use in mechanical ventilation.

Figure 3: Purging or extraction fan with flexible duct.

Illustration of an industrial mechanical ventilation extraction unit.

Figure 4: Mechanical extraction ventilation system with filtration.