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First Alert CO400

First AlertCO alarmsRetrieved 7 November 2026

A CO alarm warns you; it doesn't make a generator or fuel heater safe indoors. Read the generator and carbon monoxide safety guide.

The First Alert CO400 is a battery-powered CO alarm listed to UL 2034.[1]

Fits: CO warning with a replaceable battery rather than a sealed battery.

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Specs

SpecFirst Alert figure
ListingListed to UL 2034 Standard[1]
Power source1 replaceable 9V battery[1]
Battery life claimNot listed by First Alert[1]
DisplayNo digital display is listed by First Alert[1]
End-of-life signalEnd-of-life warning[1]
Alarm volume85 dB at 10 feet[1]

Good to know

  • First Alert lists an electrochemical CO sensor and a test/silence button.[1]
  • A low-battery light and alarm warn when battery power is low.[1]
  • BlackoutSmart has not tested this product; specifications and claims come from the sources below.

Price

First Alert's site listed $24.99 on 2026-11-07. Prices change, so check the current price.[1]

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How we handle prices