What device indicates the percentage of oxygen present in a test atmosphere by reacting with the electrolyte?

The device that indicates the percentage of oxygen present in a test atmosphere by reacting with the electrolyte is the oxygen sensor. This instrument operates on the principle of electrochemical reactions, where the presence of oxygen causes a chemical change within the sensor's electrolyte. As the oxygen concentration varies, it produces a measurable electrical signal that reflects the corresponding oxygen levels in the surrounding air.

Other options, while they may relate to oxygen or its production, do not serve the specific function of measuring oxygen concentration in the atmosphere. An oxygen generator, for instance, actively produces oxygen rather than measuring it. An oxygenator is a device used in medical applications to increase the oxygen content in blood, and an oxygen condenser is typically involved in processes focusing on cooling or condensing gases rather than measuring oxygen levels. Understanding the function and principle of the oxygen sensor is crucial for anyone involved in confined space operations, as proper atmospheric monitoring is vital for safety and rescue protocols.