NFPA 1991 focuses on protective ensembles for which type of emergencies?

NFPA 1991 specifically addresses performance criteria for protective ensembles designed for activities involving hazardous materials. This standard ensures that the materials and designs of protective gear can effectively shield wearers from chemical, biological, radiological, and nuclear (CBRN) agents that may be present during hazardous material emergencies. The emphasis on fit, durability, and functionality within this standard helps ensure the safety of individuals responding to or managing incidents involving hazardous substances.

Each of the other options pertains to different types of emergencies, but NFPA 1991 is uniquely aimed at providing guidance for scenarios where protection from toxic or hazardous materials is paramount, thereby ensuring that those dealing with such incidents can perform their duties with an appropriate level of safety and effectiveness.