Which of the following best describes the main classes of SHS agents typically considered in NICET scope?

• A. Inert gas systems and water-based sprinklers
• B. Clean agents, inert gas systems, and carbon dioxide-based systems
• C. Only inert gas
• D. Only clean agents

Answer: (B)

The main idea here is how SHS extinguishing agents are categorized for NICET scope. In this context, three main classes are recognized: clean agents (chemical agents that extinguish fires with minimal residue and are suitable for occupied spaces), inert gas systems (gas mixtures that dilute the atmosphere to suppress flame while keeping occupants breathing), and carbon dioxide-based systems (CO2 reductions in the space to stop the fire). Water-based sprinkler systems are not SHS agents; they belong to a different suppression category. So, describing SHS agents as clean agents, inert gas systems, and carbon dioxide-based systems best matches NICET’s typical scope.