Addressable panels identify the specific detector in alarm; conventional panels identify only the zone. NFPA 72 and most local codes require addressable for buildings above certain occupancy or square-footage thresholds, but the practical break-even is around 20-30 detectors. Above that count, addressable saves diagnostic and maintenance time. Below it, conventional is often the budget-friendly choice.

Photoelectric detectors respond fastest to smoldering fires (cigarettes, electrical wiring); ionization detectors respond fastest to flaming fires (paper, kitchen). Modern dual-sensor detectors include both technologies and meet UL 268 7th edition requirements. Most jurisdictions now require dual-sensor or photoelectric for new commercial installations. Ionization-only is being phased out due to nuisance-alarm performance in cooking and shower-steam scenarios.

NFPA 72 requires annual inspection and testing of the entire system, semiannual battery testing, and monthly visual inspection of the panel. Local AHJ requirements often mandate documentation and a service contract with a licensed contractor. The owner-of-record bears legal responsibility for inspections — missing an annual inspection exposes the owner to fines and insurance claim denial.

Yes if the HVAC system exceeds 2,000 CFM (commercial threshold) — code requires duct smoke detectors that shut down the HVAC to prevent smoke distribution during a fire. Confirm CFM rating against local code thresholds; many jurisdictions require duct detection on smaller systems serving multiple-occupancy buildings. Duct detectors must report to the building's fire alarm panel.

NFPA 72 requires 24 hours of standby operation plus 5 minutes in full alarm. Calculate panel current draw under both conditions, then specify a battery with adequate Ah capacity. Lead-acid batteries lose capacity in cold environments — derate by 20% for unconditioned spaces. Replace batteries every 4-5 years even if they test good; failure rates climb steeply after year 5.