Before entering excavations greater than 4 feet deep, what must be done regarding the atmosphere?

Before entering excavations greater than 4 feet deep, it is crucial to test for oxygen deficiency. This is because underground environments can contain hazardous gases, which may displace oxygen and lead to an unsafe atmosphere for workers. Testing for oxygen levels ensures that the concentration is sufficient for human health, allowing for safe entry into the excavation.

While other factors like moisture levels, temperature, and noise levels are important to consider in various contexts, they do not specifically address the immediate risks associated with confined or deep spaces, where oxygen depletion can occur. Ensuring adequate oxygen is present is a critical safety measure that prevents asphyxiation and promotes a safe working environment. This makes testing for oxygen deficiency the most pertinent requirement prior to entering deep excavations.