With low oxygen being a significant cause of death in confined spaces, it’s important that you continuously measure oxygen levels. OSHA dictates that the minimum "safe level" of oxygen in a confined space is 19.5 percent and the maximum is 23.5 percent. If the oxygen concentration in a confined space surpasses 23.5 percent, the space is too oxygen-rich and could ignite combustible gases. On the other hand, low oxygen levels impair judgment and coordination. Extremely low levels of oxygen cause nausea, vomiting, and loss of consciousness. When oxygen levels are too low, that typically means another gas is displacing it. In these instances, it’s important to know what gas is displacing oxygen and why.