Final answer:
The year by which homes must have smoke detectors varies by locality, with many building codes requiring them after the 1970s. Smoke detectors use americium-241, which through α-decay, helps detect smoke by interrupting a current flowing between metal plates.
Step-by-step explanation:
The specific year by which homes must have at least 1 smoke detector installed varies by location since building codes are often established by local governments.
However, it is widely accepted that homes built after the 1970s are generally required to have smoke detectors due to the model building codes adopted by various jurisdictions over time. These safety requirements, including the presence of smoke detectors, running water, working ventilation and heating systems, and properly installed electrical wiring, ensure the safety of inhabitants.
Understanding Smoke Detectors
Most smoke detectors contain a radioactive element called americium-241. Americium-241 undergoes α-decay, which is utilized in the detection mechanism. The radioactivity of americium ionizes the air between two metal plates in the detector, allowing a small current to flow. When smoke interferes with this current, the drop in current flow triggers an alarm, alerting residents to the potential presence of fire.
It's important to note that while building codes can be intricate and adapting to them might incur costs, they play a crucial role in protecting residents from hazards such as fires, structural collapses, and other safety risks.