What is Grade D air?

Grade D air refers to a specific quality of air that is deemed safe for breathing in various occupational settings, especially those related to construction and environmental work. The designation is crucial in contexts where workers may be exposed to hazardous conditions, as it establishes a baseline for acceptable oxygen levels necessary to ensure the safety and health of individuals.

The correct answer identifies Grade D air as having an oxygen concentration range of 19.5% to 23.5%. This range is significant because it ensures that there is sufficient oxygen for normal respiratory function while also maintaining the air quality to avoid potential health risks associated with lower oxygen levels, which can lead to asphyxiation or other harmful effects. The specification also helps differentiate safe air from atmospheres where the oxygen concentration drops below the recommended thresholds.

In contrast, options that suggest other concentrations either fall outside this acceptable range or do not accurately define the safety standards for breathable air in environments where asbestos or other hazardous materials may be present. Understanding Grade D air is essential for ensuring the safety of workers and complying with health regulations in various fields, primarily those involving asbestos abatement or similar hazardous material handling.