Which category includes activities, systems, or equipment whose failure is not likely to cause injury but can cause discomfort?

The correct answer is Category 3. This category is specifically defined to include activities, systems, or equipment that, while not critical to patient safety, can still negatively affect patient comfort and care quality if they fail. Understanding the categories within NFPA 99 is essential for distinguishing between various levels of risk associated with medical gas systems and other healthcare equipment.

Category 3 systems are generally associated with equipment that is not essential for sustaining life but can still provide significant comfort or support to patients. An example might include certain types of diagnostic equipment or supplemental systems that, if they fail, would lead to inconveniences or distress for patients, but not pose a direct threat to their safety.

This classification highlights the importance of maintaining a high standard of care and comfort in healthcare settings, ensuring that even non-critical systems are regularly inspected and maintained.