Which of the following oxygen levels indicates a serious risk of fire explosion hazard?

The correct answer is based on the understanding of how oxygen levels in the environment contribute to fire hazards. Under standard atmospheric conditions, the normal oxygen level is approximately 20.8%. When oxygen levels increase beyond this normal range, the risk of fire and explosions significantly escalates.

When oxygen concentration reaches about 23.5%, it is considered to be in a range that presents a serious fire and explosion hazard. At this level, materials that would not normally ignite in regular atmospheric conditions could catch fire more easily and burn more vigorously.

In contrast, lower oxygen levels, such as 19.5% and 16%, reduce the risk of fire hazards. Oxygen levels below 19.5% are typically classified as oxygen-deficient environments, which pose risks primarily related to asphyxiation rather than combustion. Thus, while excessive oxygen can enhance fire risk, diminished oxygen levels result in fewer combustion-related concerns, underscoring the significance of the specified level of 23.5% as a critical threshold for fire risk assessment.