What must be consulted primarily during emergencies or infrequently?

The correct answer is Material Safety Data Sheets (MSDS), now commonly referred to as Safety Data Sheets (SDS). These documents are essential resources that provide detailed information on the properties of a particular chemical substance or mixture. During emergencies, such as spills, exposures, or fires involving hazardous materials, consulting the SDS is crucial because it includes vital information on handling, emergency response measures, health hazards, and first aid procedures.

SDSs are designed to be readily accessible in situations where immediate response to a chemical hazard is necessary. They outline specific actions to take in emergencies, including firefighting measures, containment procedures, and protective equipment required. This makes SDS an invaluable resource when quick decisions are needed to ensure safety and mitigate harm.

In contrast, other options play different roles in safety and emergency management. Incident response plans are more comprehensive guidelines for managing incidents rather than specific chemical hazards. Safety drills are practice sessions intended to prepare individuals for emergencies but do not provide detailed chemical-specific information. Equipment manuals inform users about the proper operation of machinery but lack the immediate hazard-specific data needed during a chemical emergency. This distinction highlights why the SDS is the primary source to consult in emergencies involving hazardous materials.