What might indicate an oxygen-deficient atmosphere in a confined space?

The presence of rust accumulation can indicate an oxygen-deficient atmosphere in a confined space because iron oxide (rust) forms when there is insufficient oxygen available for the metal to corrode properly. When metal rusts, it typically occurs in the presence of moisture and limited oxygen, which reflects an environment lacking adequate breathable air. A confined space may have limited ventilation, leading to reduced oxygen levels and subsequently resulting in rust formation on metal surfaces.

In contrast, a strong odor typically indicates the presence of gases or chemicals rather than a direct indication of oxygen levels. Dust particles do not provide a reliable sign of oxygen deficiency; they may originate from various sources unrelated to oxygen levels. Similarly, color changes in the environment can occur for various reasons, such as contamination or chemical reactions, and do not specifically indicate oxygen deficiency. Therefore, rust accumulation by itself is a more direct sign of a potentially unsafe atmosphere due to low oxygen levels.