Why are excavations with sloughing walls, grain silos, and trenches categorized as permit-required confined spaces?

Permit-required confined spaces are classified based on the potential hazards they present to workers. In the case of excavations with sloughing walls, grain silos, and trenches, the primary reason for this classification is their potential for caving in or engulfment.

This potential for caving in occurs in excavations or trenches where the walls can collapse unexpectedly, creating a hazardous situation that can trap or suffocate an individual. Similarly, in grain silos, there is a risk of engulfment due to loose grain that can shift, burying a worker who may be in the silo. The dynamics of these environments present serious physical hazards, necessitating the need for a permit and specific safety measures before entry.

While temporary storage, location underground, and ventilation are factors to consider in confined spaces, they do not define the specific hazards that require a permit. The defining characteristic of a permit-required confined space is the risk of cave-ins or engulfment, which can lead to severe injury or fatality if proper precautions are not taken.