Before entering a confined space, what is essential to test regarding oxygen levels?

It is crucial to test oxygen levels in a confined space to ensure they are within the safe range for human occupancy, which is typically between 19.5% and 23.5%. This range indicates that there is enough oxygen for breathing without the risk of hypoxia (insufficient oxygen) or hyperoxia (excess oxygen). Oxygen concentrations below 19.5% can lead to symptoms of oxygen deficiency, while levels above 23.5% can pose a risk of fire or explosion due to high reactivity. Hence, determining that the oxygen levels are between the minimum and maximum limits is essential for ensuring the safety of personnel entering the confined space.