Final answer:
Group I-3 occupancies are required to have manual fire alarms and automatic smoke detection systems installed to alert occupants of potential fire hazards. The smoke detectors use Am-241 in ionization chambers to sense smoke and trigger the alarm.
Step-by-step explanation:
Group I-3 occupancies, which refer to buildings where occupants may need assistance in evacuating, are required to have a manual fire alarm system and automatic smoke detection system installed to alert people of potential fire hazards. The manual fire alarm system allows occupants to manually activate the alarm in case of a fire emergency, while the automatic smoke detection system uses ionization-type smoke detectors to sense smoke and trigger an alarm.
Am-241, an alpha emitter with a half-life of 458 years, is used in the ionization chamber of smoke detectors. When smoke enters the chamber, it impedes the movement of ions and reduces the conductivity of the air, causing a drop in the current and triggering the alarm. This requirement is in place to ensure the safety of occupants in these specific types of buildings by providing early detection of potential fires and alerting them to take necessary actions for evacuation.