Safety Alert

Stacking of baled recycled material in the waste sector

The HSA is issuing this safety alert following recent fatalities where employees were fatally injured when stacks of recycled material collapsed on top of them.

If recycled material is not stacked correctly it can cause the stack to become unstable and collapse leading to devastating consequences if they fall on persons in the vicinity of the collapse. The following two photographs are examples of poorly stacked bales.

paper-bales plastic-bales

Factors affecting stack stability

  • The size, weight, shape and density of the bales will have an impact on the stability of the stacked material.
  • The type of material in the bale will need to be considered when choosing how the baled material is to be stacked. 
  • Heat, cold and sunlight may affect the material and cause it to break down, weakening the bale and causing it to break apart.
  • Placing heavy or large bales on the top of stacks can cause the stacks to topple over.
  • Bale strapping – Straps can break if they are over loaded. If they are too loose this can cause a bale to come apart weakening the stack and causing it to fall.  Straps can also break down over time if left exposed to the elements.  Metal straps may rust.
  • Bales may contain unseen material that may break down over time affecting their stability; this can weaken a strapped bale and cause it to deform.  

Managing stacking

1.    The employer must carry out a risk assessment to identify the hazards associated with stacking the various type of recycled material. This material could include but is not limited to the following; waste plastic sheeting, plastic bags, card board, plastic bottles and milk containers.

2.    The employer must then put in place control measure to reduce the risk. These control measures should consider the following.

  • Ensure that the material is stacked on level ground that is free from debris and is properly drained to comply with environmental standards.

  • Construct the stacks from bales of similar size and weight, failing that the bigger heavier bales should be stacked on the bottom with smaller lighter bales on top.

  • Ideally the stacked bales should be contained on three sides by a wall or other barrier designed to withstand the weight of the stack if it collapses. Bales on the open side of this stack should be stepped back. See figure 1.

  • In the case of single stacks, avoid stacking bales vertically one of top of the other. See photograph 3. They should be stacked in a pyramid formation. See Figure 2 and 3

  • Interlocking the bales as the stack is being constructed will improve stability.

  • Placing boards in between layers can also improve the stack stability.

  • The outer layers of the stacks should have lengths of timber placed on the edges so that the bales will lean inward.

  • Control measures need to be put in place to protect the stacks from being struck by moving vehicles.

  • A written procedure should be put in place to deal with stacks that have become unstable or that are in danger of collapsing.

  • Exclude pedestrians from the stacking area. Put a traffic management plan in place that focuses on segregating vehicle movements from pedestrians. Plan the stacking operations so that one way systems can be utilised where possible.

  • Appropriate vehicles should only be used for stacking and moving the bales. These vehicles should be fitted with falling object protection systems. When selecting the type of vehicle to be used, consideration must be given to,

    - the type of material to be lifted,
    - its weight,
    - type of stack being constructed,
    - the distance it has to reach.

  • The vehicle should be able to deal with stacks that have collapsed or bales that have fallen. Vehicles must be fitted with warning devices and have visual aids to reduce blind spots on the vehicle.
  • Consideration must be given to the separation distances between stacks so that in the event of a fire it does not spread.
  • Consideration must be given to the separation distances between stacks to ensure that vehicles have adequate room to manoeuvre.

Training and instruction

  • Ensure that the risk assessment and control measure are brought to the attention of the employees.
  • Ensure that forklift drivers and other machine operators have appropriate training.
  • Ensure that employees are instructed on how to deal with stacks that have become unstable or are in danger of collapse.
  • Ensure that employees have training on fire and emergency procedures.


Photograph 3 (above)


Figure 1. Bales stacked in an area confined on three sides by a concrete wall or other suitably designed and constructed barrier.


Figure 2. Large free standing stack. Bales are stacked in a pyramid. The bales are interlocked to improve stability.


Figure 3. Bales stacked in simple pyramid formations.