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Hazard
Silos and storage tanks

Hazard Knowledge

Silos

Refer to the supplementary information about silos.

The main hazards to be considered when attending an incident with a silo are:

  • The need for enclosed space working
  • Oxygen-deficient atmosphere
  • High concentrations of carbon dioxide
  • Asphyxiation if trapped in contents
  • Associated on-site machinery
  • Explosive atmosphere
  • Unstable contents
  • Access and egress

The contents of a silo may act in a fluid manner and may not be load bearing. There is a phenomenon in silos known as bridging; this is where the material appears to be solid but has actually formed a bridge above a void in the contents. Fire and rescue service personnel should not trust that seemingly solid surfaces in silos will be able to bear their weight.

The nature of the goods stored within silos may create a toxic, flammable, oxygen deficient or explosive atmosphere. Opening up a hatch or door may create an explosive mixture.

Oxygen limiting silos or controlled atmosphere silos have a greater risk of backdraft or explosion when they are involved in a fire.

When involved in a fire or suspected fire, opening any doors or hatches could result in a heat blast. For further information, see National Operational Guidance: Fires and firefighting.

Applying water or foam into a silo may result in the contents swelling. Due to the increase in weight, volume and pressure on internal walls, this could lead to structural collapse of the silo.

Many of the contents stored within a silo produce dust. Refer to the hazard for combustible dust.

Gaining access to a silo may involve working at height, with a hazard of fire and rescue service personnel or their equipment falling inside or outside of the silo.

See National Operational Guidance: Subsurface, height, structures and confined spaces – Work at height

Silos usually have internal and external machinery including:

  • Augers, which sweep the contents inside the silo
  • Screw feeders
  • Conveyer belts
  • Paddles
  • Suction piping
  • Mixing blades

See National Operational Guidance: Industry: Machinery

The nature of construction limits access and egress to and from silos and storage tanks, and they will lack natural light and ventilation. See national Operational Guidance: Industry supplementary information: Silos.

Storage tanks

Storage tanks are used in many industries, mainly for the storage of liquids including:

  • Fuels
  • Water
  • Chemicals
  • Liquid foodstuffs

Storage tanks may be constructed of plastic, fibreglass or metal. Some tanks have covers that are not load bearing.

Working near tanks containing liquids presents similar hazards to working near water. Therefore, the guidance contained in National Operational Guidance: Water rescues and flooding may need to be applied.