What oxygen level is considered dangerous and can lead to loss of consciousness?

An oxygen level of 8-12% is indeed considered dangerous and can lead to serious health effects, including loss of consciousness. At these low concentrations, the body is unable to get sufficient oxygen to function properly, which can result in hypoxia, a condition where the tissues in the body do not receive enough oxygen. Symptoms of hypoxia can include dizziness, confusion, and ultimately loss of consciousness if exposure continues.

In contrast, the other options reflect levels of oxygen that are either within safe limits or only marginally low. A concentration of 16% is often seen as low but not immediately life-threatening. The options of 19.5% and 20.8% indicate normal atmospheric oxygen levels, which are safe for human breathing. Hence, understanding the critical thresholds for oxygen levels is vital in assessing safety in various environments, especially when dealing with confined spaces or hazardous conditions.