A facility manager holding ten years of clean annual inspection reports for a fire alarm system tends to read them as proof that nothing changes. Same panel, same devices, same line at the bottom: no deficiencies noted. What that stack of paper does not show is the trend underneath it. The best evidence available on how fire alarm components age comes from outside the United States, and it says the defect rate does not stay flat. It rises earliest in the parts built to sense smoke and make noise.

That evidence is a 2024 peer-reviewed analysis of 4,629 fire alarm inspection reports from Germany, published in the journal Safety (Steiner, Veit, et al., “Defect Trends in Fire Alarm Systems: A Basis for Risk-Based Inspection Approaches,” MDPI, Vol. 10, Issue 4, Article 95, November 2024, https://doi.org/10.3390/safety10040095). Those systems were inspected between 2020 and 2022 on Germany’s three-year test cycle, a different schedule from anything used under NFPA 72. No published US peer-reviewed study measures fire alarm defect rates by system age the way this one does. Nobody has run it on American systems, under American testing frequencies, in American buildings. What follows treats the German findings as the best available evidence on how components age, not as a US statistic wearing a different label.

The stakes for keeping detection working are documented separately. Automatic sprinklers, where present, cut the civilian fire death rate by 90 percent compared to properties with no automatic extinguishing system, and operate in 92 percent of fires large enough to trigger them (NFPA Research, “U.S. Experience with Sprinklers,” April 2024, https://www.nfpa.org/education-and-research/research/nfpa-research/fire-statistical-reports/us-experience-with-sprinklers). Detectors and notification appliances do that job on the front end, and only if the device works when called on. A defect trend concentrated in detectors and horns sits in the part of the system with the least room to fail quietly.

What the study found, and where it stops

The German researchers found that defect frequency rose after ten years in service, most sharply for acoustic signaling devices (horns, sounders, and similar notification appliances) and for detectors. The increase was more pronounced under demanding environmental conditions: systems exposed to more heat, dust, humidity, or vibration aged faster than systems in cleaner settings. Larger systems drifted further from a defect-free result as they grew, a pattern covered on its own below.

A rise in defect frequency after year ten is not the same claim as a system being due for replacement at year ten. The study measured how often inspectors found something wrong on a test cycle, not a service life. A facility manager should take the direction seriously, aging components fail more often and environment makes it worse, without adopting a number the research does not contain.

Which components to check first

Two categories moved first in the German data: detectors and acoustic notification devices. That tracks with how the devices work. A smoke detector has a sensing chamber that collects dust and residue over years of continuous power. A horn or sounder has a mechanical or piezo element that wears with use. NFPA 72 already treats detectors differently: sensitivity is checked within a year of installation, then on a schedule that extends as results stay clean. Notification appliances get no built-in sensitivity check; they are tested annually on a simpler question, whether they still sound or flash on demand.

The systems doing the hardest work often sit in buildings least forgiving of a failure. Operating equipment is the leading heat source in US warehouse fires, responsible for 44 percent of them, and arcing alone accounts for an estimated 14 percent of warehouse fires and 21 percent of direct property damage (NFPA Research, “Warehouse Structure Fires,” February 2025, https://www.nfpa.org/education-and-research/research/nfpa-research/fire-statistical-reports/warehouse-structure-fires). Heat, electrical stress, and continuous operation are the same conditions the German study tied to faster defect growth. A device on a warehouse floor ages inside the environment that produces the fires it exists to catch.

How NFPA 72 testing frequency interacts with an aging system

NFPA 72 does not test every device on the same interval. Control equipment connected to a supervising station is inspected initially and annually; equipment without that connection is inspected quarterly. Waterflow devices, tamper switches, and other supervisory signal devices are tested quarterly to semiannually. Notification appliances are tested annually. Smoke detector sensitivity is checked within a year of installation, then every other year, extending to every five years once two consecutive tests come back clean (NFPA 72, National Fire Alarm and Signaling Code, current 2022 edition, Chapter 14, inspection, testing, and maintenance requirements, https://www.nfpa.org/codes-and-standards/nfpa-72-standard-development/72).

That extension schedule assumes two clean tests predict a third. The German data complicates that once a system passes ten years: a five-year gap on a fifteen-year-old detector is a longer stretch of unmonitored time on a device statistically more likely to be developing a problem. NFPA 72 does not vary its schedule by system age, only by device history. Relying on the extended interval on an older system is a judgment call the code itself does not make.

NFPA 72 is also not the only schedule in play. OSHA’s 29 CFR 1910.165(d) requires employee alarm systems to be kept in operating condition except during repairs, and sets its own intervals: non-supervised systems tested for reliability and adequacy every two months, using a different actuation device each test, and supervised systems installed after January 1, 1981 tested at least annually. That two-month loop is shorter than anything in NFPA 72, and on an aging system it is the check most likely to catch a failing device first.

Why larger systems drift further from a clean report

The same study found that as fire alarm systems grew larger, meaning more devices and more zones, the share of inspections coming back completely defect-free went down. Part of that is arithmetic as much as aging. A system with 40 devices has 40 chances for one to fail a test; a system with several thousand devices has several thousand chances. A large system is not more likely to fail as a whole. It is more likely to return at least one flagged device on any given cycle, because it has more devices to flag.

Framing the repair-versus-replace decision

A stack of inspection reports is more useful read as a trend than as a checklist. Pull several years, not just the most recent one, and start with where the failures land. Are the same devices or the same loop showing up repeatedly, or is the pattern spread evenly across the building? A cluster in one loop points to a wiring or environmental problem. A flat, low rate of minor deficiencies is ordinary wear; a rate that climbs year over year, especially concentrated in detectors or notification devices, matches the pattern the German research associated with systems past the ten-year mark. Environment belongs in the same review: a conditioned office ages differently than a manufacturing floor or an unconditioned warehouse.

Two more questions belong in the file before a decision gets made. Are the repairs correcting the device itself, or working around a control panel manufactured a decade or more ago whose replacement components may no longer be in production? And what does the authority having jurisdiction or the insurance carrier require if a major repair happens? Some jurisdictions and policy endorsements expect like-for-like restoration or documented compensating measures, which changes the comparison.

None of that produces a single number that says replace now. It produces a comparison: the cost of continuing to chase repairs on a system with a rising, concentrated defect pattern, against the cost of a planned upgrade on a schedule the facility manager sets, rather than at the moment of a failed annual test.

What device-level records show that a pass-fail report does not

A standard annual inspection report answers one question: did the system pass. It does not show which device failed last year, whether it failed the year before too, or whether failures cluster by manufacture date, floor, or exposure. That distinction separates a compliance record from a maintenance history.

Versys uses Building Reports software, which inventories every device with a barcode system rather than treating the panel as a single pass-fail unit. That gives a facility manager visibility into individual device history and failure patterns over time, the kind of device-level detail the German researchers relied on to identify which components degrade first. A pass-fail summary says the system worked on the day of the test. A device-level record across several cycles says whether it is trending toward the pattern the research describes, and points to which devices to look at first.

What this looks like handled well

For a Kentucky or Southern Indiana facility with a system installed in the mid-2010s or earlier, the task is not guessing at a universal expiration date, which the research does not support. The task is reading the record: which devices are failing, how often, whether the pattern matches the acoustic-device and detector trend the German study flagged, and whether the building’s environment is accelerating it. The company handles ongoing inspection, testing, and repair on Silent Knight, Firelite, and proprietary systems across the region, and keeps that device-level record through Building Reports rather than a single pass-fail line per year.

A facility manager sitting on ten or more years of inspection reports can start by asking Versys to pull the device-level history behind those reports and identify where the defect pattern sits, before deciding what gets fixed and what gets planned for replacement. Call (270) 358-2200.