Why must passengers be briefed on smoking regulations?

Passengers must be briefed on smoking regulations primarily due to potential fire hazards in confined spaces. Airplanes are enclosed environments where the risk of fire can lead to catastrophic consequences. Smoking onboard may introduce open flames or lit materials, creating serious fire risks in a setting where oxygen is prevalent and materials can ignite quickly. Briefing passengers about smoking regulations emphasizes safety and the importance of preventing situations that could lead to onboard fires, protecting everyone within the aircraft. This safety measure is especially crucial during critical phases of flight, such as takeoff and landing, when the aircraft is most vulnerable.