A trench must be tested for hazardous atmosphere if its depth exceeds what measurement?

A trench must be tested for hazardous atmospheres if its depth exceeds 4 feet because this is the depth at which the Occupational Safety and Health Administration (OSHA) regulations require additional safety measures to prevent potential hazards. At depths greater than 4 feet, there is an increased risk of hazardous atmospheres, such as the accumulation of toxic gases or insufficient oxygen levels, which can pose serious health risks to workers. Testing for these potential hazards is crucial for ensuring the safety of personnel working in or around these trenches. This requirement underscores the importance of maintaining a safe work environment, especially in deeper excavations where conditions can quickly change.