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Kidde · Hardwired smoke alarm

Kidde i12040 / i12040A: age, expiry and what replaces it

Also printed as: i12040A

Quick answer

Kidde's hardwired ionization smoke alarm with a single Test/Hush button and a 9-volt backup battery. It shares a user guide with the i12080A (the same alarm plus a battery-powered safety light). Replace it ten years after the date code on its back; the 20-9003 adapter lets a newer Kidde alarm reuse its wiring plug.

Last checked

At a glance

Sensor type
Ionization1
Power
Wired to 120 V AC household power, with a 9 V backup battery included1
Same guide covers
i12040A and i12080A; the i12080A adds a battery-powered LED safety light2
Backup battery
The guide lists the approved 9 V batteries (for example Energizer 522 or Duracell MN1604/MX1604) and rules out lithium batteries2
Where the date is
The date code is printed on the back of the alarm, as is the model number2
When to replace
Ten years from the date code, the interval the guide attributes to both Kidde and NFPA2
Low-battery signal
A chirp about every 30–40 seconds when the backup battery runs low2
Silencing a low-battery chirp
The guide describes a low-battery Hush that quiets the chirp for about 13 hours; it is a reminder window, not a fix2
Interconnect
Up to 24 Kidde devices on one wired loop, 18 of which can set off the rest (smoke, CO and heat alarms)1
Smoke-alarm limit per loop
No more than 12 smoke alarms (18 alarms in total) on one system, which the guide gives as the NFPA limit2
Warranty
10-year limited1
Ordering number
210063781

Replacing it

Replacement named by Kidde
Kidde's i12040 page did not name a replacement model when we checked. Kidde's replacement guide says discontinued models show their replacement on the product page found through its model search.3
Keep the old wiring plug
The 20-9003 adapter guide lists i12040 and i12040A as older Kidde harnesses it can connect to a new Kidde alarm with the newer connector4
Check the pairing first
Kidde warns the adapter only works for listed old/new model pairs; do not go by plug shape or brand alone5
Mixing brands on one loop
Only alarms on Kidde's tested list should share the interconnect wire; Kidde says unlisted equipment could cause nuisance alarms, failure to alarm, or damage6
Recalls
Search CPSC's recall list for your exact model before reusing or reselling an alarm7

Related models

Other models that cite the same adapter

Each link goes to another model page that cites the same adapter document. Whether two alarms can share a plug is answered in that document, on the model page.

Common questions

Where is the date on a Kidde i12040?

The date code is printed on the back of the alarm, as is the model number2

When should a Kidde i12040 be replaced?

Ten years from the date code, the interval the guide attributes to both Kidde and NFPA2

What replaces the Kidde i12040?

Kidde's i12040 page did not name a replacement model when we checked. Kidde's replacement guide says discontinued models show their replacement on the product page found through its model search.3

Which adapter guide lists the Kidde i12040?

The 20-9003 adapter guide lists i12040 and i12040A as older Kidde harnesses it can connect to a new Kidde alarm with the newer connector4

Sources

  1. Kidde — AC Hardwired Interconnect Smoke Alarm with Hush i12040 (product page) checked 2026-10-31
  2. Kidde — i12040A / i12080A Smoke Alarm User Guide (PDF) checked 2026-10-31
  3. Kidde — Alarm Replacement Guide checked 2026-10-31
  4. Kidde — 20-9003 Wiring Adapter User Guide (PDF) checked 2026-10-31
  5. Kidde — Quick Connect Adapter 20-9003 (product page) checked 2026-10-31
  6. Kidde — What Other Products Will Kidde Alarms Interconnect With? checked 2026-10-31
  7. CPSC — Recalls & Product Safety Warnings checked 2026-10-31

Facts are restated in our own words. If a source page changes, the "checked" date tells you how fresh our reading is. Spot something out of date? Open an issue on GitHub.

Published October 31, 2026. Part of the Kidde brand hub.