Gravity-open vents are described as which of the following?

Gravity-open vents are described as which of the following?

• A. They are made of metal and rise toward the ceiling when heated.
• B. They require active mechanical power to operate.
• C. They are closed by smoke dampers.
• D. They are gravity-open and typically made of plastic that can soften from heat and fall down.

Answer: (D)

Gravity-open vents operate without any powered mechanism, relying on gravity to hold the vent open under normal conditions and to respond passively in a fire situation. They are often constructed with plastic components, which can soften when exposed to high heat, causing the vent to sag or fall closed and reducing ventilation when it’s most needed. This combination—passive, gravity-driven operation and vulnerable plastic materials—fits the description of a gravity-open vent, making it the best answer. The other descriptions describe mechanisms or materials that don’t align with how gravity-open vents function.

Gravity-open vents operate without any powered mechanism, relying on gravity to hold the vent open under normal conditions and to respond passively in a fire situation. They are often constructed with plastic components, which can soften when exposed to high heat, causing the vent to sag or fall closed and reducing ventilation when it’s most needed. This combination—passive, gravity-driven operation and vulnerable plastic materials—fits the description of a gravity-open vent, making it the best answer. The other descriptions describe mechanisms or materials that don’t align with how gravity-open vents function.