Final answer:
NFPA 72 requires household smoke alarm systems to be tested according to the manufacturer's instructions, which is often recommended as monthly testing. Smoke detectors use americium-241 to create an ionization process that, when disrupted by smoke, triggers an alarm.
Step-by-step explanation:
According to the NFPA 72, household smoke alarm systems should be tested following the manufacturer's published instructions at least as often as the manufacturer recommends. For most household detectors, this typically means testing the alarms monthly to ensure they are functioning correctly. The typical smoke detector uses an electric circuit with a small amount of the radioactive element americium-241 to ionize air between two metal plates. This ionization creates a consistent electric current. When smoke particles interrupt this current by reducing air conductivity, the drop in current triggers the alarm, signaling potential fire in the household. It's important to also maintain proper ventilation in the home and use carbon monoxide detectors to enhance safety measures.