What is an indication of a poorly ventilated confined space?

A concentration of oxygen below 19.5% is a significant indicator of a poorly ventilated confined space. In a normal atmosphere, oxygen levels are around 21%. When levels fall below 19.5%, it suggests that there is not enough fresh air circulating within the space, which could lead to asphyxiation or other health hazards. This reduced oxygen can occur due to various factors, such as the consumption of oxygen by combustion or chemical reactions taking place within the space. Proper ventilation is essential to ensure that oxygen levels remain safe, minimizing the risk of dangerous situations for individuals working in confined areas.

Other options may not necessarily indicate poor ventilation. For example, high oxygen levels could point to active ventilation or an introduction of pure oxygen. The presence of dust does not directly assess the air quality regarding oxygen levels, and constant air movement might even suggest that ventilation is adequate or functioning effectively. Thus, a low oxygen concentration is the definitive indicator of inadequate ventilation in such environments.