What is the primary purpose of a self-rescuer (SCSR) in mining?

The primary purpose of a self-rescuer, or self-contained self-rescuer (SCSR), in mining is to supply oxygen in emergencies. These devices are essential for miners who may become trapped in environments with toxic gases or smoke, as they allow miners to breathe in life-threatening situations where the normal atmosphere has been compromised.

SCSRs contain a chemical reaction that generates oxygen while simultaneously removing carbon dioxide, enabling miners to survive until they can reach safety or until help arrives. This function is critical in underground mining where the risk of encountering hazardous conditions such as explosions or toxic gas leaks is significant.

In contrast, signaling for help, providing light, and protection against gas leaks are important safety measures, but they do not address the immediate need for breathable air in an emergency situation, which is the core function of an SCSR. Thus, the correct answer highlights the most crucial aspect of the device in safeguarding miners' lives during respiratory emergencies.