Guide

Fusible links and detection devices: who replaces them and how often

Updated 2026-10-13

Those small metal links in the hood and at the duct entrance are the automatic heat detectors for most wet-chemical systems. Grease coats them. Heat ages them. Leaving last year’s links in place is a common inspection finding — and it is a suppression job, not a grease-clean job. This page is the operator split: cadence, who may touch them, and what belongs on the service tag.

Short answer Secondary NFPA 96 text (and NFPA 17A) requires metal-alloy fusible links — and metal-alloy automatic sprinklers used as detectors — to be replaced at least semiannually. Replacement elements must be listed and match the temperature rating unless readings justify a change. Year of manufacture and installation date go on the system inspection tag; removed links are destroyed. Bulb-type detectors and non-metal-alloy fusible links are examined and cleaned or replaced at least annually. Fire-damper fusible links on the exhaust path are also replaced at least semiannually by a certified person acceptable to the AHJ. The hood cleaner protects links during a clean; a licensed fire-protection technician does the replace-and-tag work. See suppression vs hood cleaning.

Replacement schedule (secondary NFPA 96 / 17A)

Device	Typical requirement (secondary)	Who
Metal-alloy fusible links on the extinguishing system	Replace at least every 6 months (NFPA 96 §12.2.4 pattern)	Licensed / factory-trained suppression tech
Metal-alloy automatic sprinklers used as detectors	Same semiannual replace rule	Suppression tech
Bulb-type detectors / non-metal-alloy fusible links	Examine and clean or replace at least annually	Suppression tech
Fusible links on fire damper assemblies	Replace at least semiannually (or sooner as needed) by a certified person acceptable to the AHJ	Person your AHJ accepts for damper work — confirm locally
High-volume / heavy grease kitchens	Code minimum is still 6 months; trade practice often replaces sooner when grease load is high	Ask your suppression contractor; do not invent a shorter legal interval without AHJ direction

Semiannual ITM of the extinguishing system also tests actuation and control components (manual pulls, detectors, actuators). Fusible-link replacement is part of that visit, not a kitchen-staff chore between cleans.

What must be on the tag

Year of manufacture of the installed fusible links
Date the links were installed
Installer signature or initials
Removed links destroyed — do not bag old links “for later”
Replacement links listed; same temperature rating unless the tech documents a justified change

Count links the way the listing expects: typically one over each protected appliance plus detection at the exhaust duct entrance (secondary NFPA 17A appliance/duct placement). Exact count is on the system drawings and the last ITM report — ask for that sheet if the invoice looks short.

Hood cleaning day vs suppression day

Task	Hood cleaner	Suppression contractor
Protect nozzles and links from chemicals / impact during clean	Yes — cover and restore	—
Replace metal-alloy fusible links on schedule	No	Yes
Recharge cylinder after discharge; re-tag system	No	Yes
Grease clean of hood, filters, ducts, fan	Yes	No (not their scope)
Verify nozzles capped and aimed after a clean	Restore what they moved; many kitchens still want suppression tech verify	Final word on detection line and listing

If the cleaner reports grease-caked links or a missing link, stop cooking under that hood until the suppression contractor replaces and re-tags. A cleaning sticker does not replace a suppression tag. See post-clean checks and night-before prep.

Operator checklist

Find the last suppression ITM report and the date on the fusible-link line
Confirm the next visit is scheduled inside six months from install — not “whenever the cleaner comes”
Ask for link count vs appliances + duct entrance on the quote
After hood cleaning, walk the canopy: nozzle caps on, links present, pull station clear
Keep suppression reports in a separate binder tab from grease-cleaning certificates
After any discharge or remodel that moves appliances, call suppression before the next service night — coverage and links may need redesign

Who it’s for / not for

For: Kitchen managers who confuse the cleaning sticker with the suppression tag; multi-unit ops auditing link dates across sites; landlords reviewing fire-protection ITM
Not for: DIY link replacement; designing a new UL 300 system; treating Class K extinguishers as a substitute for fixed suppression

Sources

NFPA 96 text (secondary PDF host) (§12.2.3–12.2.7 fusible links / detectors; §12.3.3 fire-damper links)
Brooks Equipment — Restaurant system ITM tech series (PDF) (secondary; 6-month ITM; replace all links; appliance + duct entrance count)
Alaska DPS — Commercial cooking fixed-temperature sensing elements (secondary training sheet; NFPA 17A / 96 semiannual metal-alloy replace; bulb-type annual clean)
Minnesota Health — Protection of kitchen cooking equipment (PDF) (secondary; semiannual service; metal-alloy links; do not apply cleaning chemicals on links)

Next step

Pull the suppression tag tonight. If the fusible-link install date is older than six months, schedule the licensed tech before the next busy weekend — do not wait for the grease cleaner’s next visit.