In the described fifth-floor scenario, which functional space includes sprayed fireproofing over the entire floor?

In the described fifth-floor scenario, which functional space includes sprayed fireproofing over the entire floor?

• A. Offices
• B. Custodial Closet
• C. Entire Air Plenum
• D. Restrooms

Answer: (C)

The main idea here is that sprayed fireproofing is used to protect the structural elements that run through concealed or functional spaces, not just the rooms people occupy. The entire air plenum is a continuous, floor-level concealed space that hosts the HVAC ductwork and returns. Because it spans the whole floor, fireproofing must cover the structural components that lie within that space so heat cannot reach those members and compromise the floor’s fire-resistance rating during a fire. Choosing the entire air plenum as the space that gets sprayed fireproofing makes sense because it ensures continuous protection across the entire floor. If sprayed fireproofing were limited to individual occupiable rooms like offices, restrooms, or a custodial closet, the structural elements in the plenum itself could remain unprotected, creating a path for fire and smoke to move between floors or spread within the building’s hidden spaces. In short, the air plenum represents the continuous floor-wide volume where fireproofing must be applied to maintain the floor’s rated fire resistance, whereas the other spaces are discrete occupancies and do not by themselves define where the spray is required to achieve that rating.

The main idea here is that sprayed fireproofing is used to protect the structural elements that run through concealed or functional spaces, not just the rooms people occupy. The entire air plenum is a continuous, floor-level concealed space that hosts the HVAC ductwork and returns. Because it spans the whole floor, fireproofing must cover the structural components that lie within that space so heat cannot reach those members and compromise the floor’s fire-resistance rating during a fire.

Choosing the entire air plenum as the space that gets sprayed fireproofing makes sense because it ensures continuous protection across the entire floor. If sprayed fireproofing were limited to individual occupiable rooms like offices, restrooms, or a custodial closet, the structural elements in the plenum itself could remain unprotected, creating a path for fire and smoke to move between floors or spread within the building’s hidden spaces.

In short, the air plenum represents the continuous floor-wide volume where fireproofing must be applied to maintain the floor’s rated fire resistance, whereas the other spaces are discrete occupancies and do not by themselves define where the spray is required to achieve that rating.