Final answer:
The built-in feature of modern buildings that can contribute to the spread of smoke and toxic gases is the HVAC system. This system, while essential for comfort and air quality, can circulate harmful substances if there's a fire or toxic release, highlighting the importance of building safety codes.
Step-by-step explanation:
Modern buildings have various systems built into them to ensure the safety and comfort of inhabitants in accordance with building codes. Among these systems, it is the HVAC systems (Heating, Ventilation, and Air Conditioning) that can unintentionally contribute to the spread of smoke and toxic gases throughout a structure. These systems are designed to circulate air and maintain indoor air quality, but in the event of a fire or the release of toxic gases, they can quickly spread these harmful substances through a building. To mitigate this issue, proper maintenance, the use of smoke detectors, and the design of the building's ventilation system are critical for ensuring they do not exacerbate hazardous conditions.
Secondhand smoke, carbon monoxide, and other dangerous substances like dry cleaning fluids and even historical uses of asbestos have heightened the awareness of air quality concerns within buildings. The role of building safety codes is to protect residents from these kinds of health hazards. While such safety features can sometimes be frustrating and costly to implement, they are essential for the well-being of building occupants.