The amount of combustible materials in a building is known as:

The term "fire-loading" specifically refers to the amount of combustible materials present in a building and is a critical concept in fire safety and prevention. Fire-loading quantifies the potential fuel available for combustion during a fire event. It is typically expressed in terms of weight per unit area (e.g., pounds per square foot) and is used to assess the risk and intensity of fire that can occur in a structure. Understanding fire-loading is essential for fire protection professionals as it helps in designing appropriate fire suppression systems, establishing safe egress routes, and determining the necessary fire-resistance ratings for structural components.

Considering the other options, "the combustion quotient" is not a widely recognized term in fire safety; it may refer to specific combustion characteristics but does not define the amount of combustible material in a building. "The fire hazard level" can describe a broader range of factors contributing to fire risk, including but not limited to the presence of combustible materials, and therefore it does not specifically indicate just the quantity of combustibles. Collectively, these other terms do not capture the precise definition that fire-loading provides.