Which of these is NOT a risk posed by inert gas when entering an enclosed space?

The correct answer is 1. Excessive oxygen.

Explanation: Inert gases, such as nitrogen, do not support combustion and do not contribute to oxygen levels. They typically replace oxygen in enclosed spaces, which can lead to oxygen deficiency (option 3) or result in the buildup of gases like carbon dioxide (option 2) and carbon monoxide (option 4), based on the activities occurring within that space. Excessive oxygen is not a risk associated with inert gases.