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HomeGuidesSmoke & CO alarms

Connected alarms, and the distinction that matters

Why a connected alarm and a tested one are different things, and why the second is not optional.

Connected and tested are different words describing different things, and only one of them is about whether the alarm will sound when it matters.

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  • Reviewed August 2026

Start here

Certified and connected are two separate things, and only one of them is required.

A certified smoke or carbon monoxide alarm has been independently tested against a published safety standard. That certification is what makes it a life-safety device, and in most places it is what the law requires.

A ceiling alarm

Being connected adds a notification on a handset. Useful; genuinely so, when nobody is home. But it adds nothing whatever to whether the alarm detects a fire.

An air quality monitor is not an alarm. It may display a carbon monoxide figure on a screen. It has not been tested to any life-safety standard, and it must never be relied on as one.

In detail

What to check on the box

The marking that matters is a certification mark, not a connectivity logo. Tap what you are looking at.

A monitor is not an alarm

What does the packaging show?

What that tells you appears underneath

General guidance on what to look for. Requirements differ by country and by tenure; check what applies where you live.

Worth knowing

Where a connected alarm genuinely helps

Once the certification question is settled, the connected part has real uses.

Alerts while you are out

When the house is empty

A conventional alarm sounds into an empty house. A connected one also reaches a handset, which is the entire argument for the category. Whether that is worth the premium depends on how often the house stands empty.

Interlinking

Interlinked alarms all sound when any one of them detects something, so a fire in a garage wakes people upstairs. This is a requirement in a growing number of places for new installations, and it can be achieved by wiring or by radio.

Radio interlinking is far easier to retrofit. What matters is that the alarms are certified to interlink with each other, which generally means staying within one manufacturer's range.

Knowing which one went off

At three in the morning, a connected system that says kitchen is meaningfully better than a house full of sound with no indication of source. Small, and appreciated at the time.

Battery warnings that arrive somewhere useful

The low-battery chirp is a national irritation. A connected alarm gives notice in the app, days before the chirping starts, which is the difference between changing a cell on a Saturday and being woken by one on a Tuesday.

What none of this changes. Connection does not improve detection. It does not extend the alarm's life; every alarm has an expiry date printed on it, commonly ten years, after which the sensor is no longer reliable and the unit must be replaced entirely. No update and no app changes that.

Practical

Where alarms go, and where they do not

Broad principles only. Requirements differ by country, and yours take precedence over anything here.

Interlinking by radio
  • Smoke alarms generally belong on ceilings, in circulation spaces, on every storey. Kitchens are usually excluded because cooking sets them off, and a heat alarm is the normal substitute there.
  • Carbon monoxide alarms belong in rooms with a fuel-burning appliance — a boiler, a gas fire, a wood burner, a range. Carbon monoxide mixes with air rather than rising cleanly, so placement guidance differs from smoke and is worth reading rather than assuming.
  • Not in bathrooms, where steam causes false alarms. Not immediately beside vents or windows, where moving air can carry smoke past.

Every alarm arrives with placement instructions specific to that model, and those instructions are the authority. Where local regulations set requirements, those come first.

This page cannot advise on your house. Where alarms are required, how many, and where they must go are questions with legal answers that vary by country, by property type and by whether you own or rent. Your fire service or local authority publishes the applicable guidance, and it is worth reading rather than inferring.

Before you buy

Questions about connected alarms

Tap a question to read the answer.

Property against life safety
+Can a connected alarm replace a certified one?Read this oneClose it againTap to read the answer

Only if it is itself certified. Plenty of connected alarms are — certification and connectivity are not in opposition, and the better products have both.

What must never happen is a certified alarm being removed in favour of an uncertified device that shows readings on a screen. That is a downgrade dressed as an upgrade.

+Do they still work if the internet is down?Read this oneClose it againTap to read the answer

A certified alarm sounds regardless. Detection and sounding are local functions and do not involve a network at all.

What stops is the notification to your handset, and on some systems the interlinking between alarms if that is routed through a hub rather than direct radio. Worth establishing which arrangement a system uses.

+What about the ten-year expiry?Read this oneClose it againTap to read the answer

Every smoke and CO alarm carries an expiry date, usually a decade from manufacture. The sensing element degrades whether or not the alarm has ever been triggered, and after that date its behaviour is no longer guaranteed.

The date is printed on the unit, generally on the back. It is worth checking on any alarm already in a house you have moved into — they are frequently older than the occupants realise.

+Is a monitor with a CO reading good enough?Read this oneClose it againTap to read the answer

No. An air quality monitor showing a carbon monoxide figure has not been tested against the standards written for life-safety alarms, and its alerting behaviour, sensitivity and reliability are not held to those requirements.

Use one for information if you like. It is not a substitute for a certified alarm and should never be installed as one.

Keep reading

Air monitors are not alarms

The same distinction, from the other direction. Worth reading alongside this.

Read the air quality guide

How we checked this

Where this comes from

  • The literature each manufacturer issues for its own equipment, which is where intended behaviour is set down
  • What Apple and Google publish for people building software, since that is where handset permissions and radio handling are described
  • The wireless specifications themselves, which govern how each band and every low-power protocol actually conducts itself
  • Opening the applications and observing them in whatever state they are in today, with every check dated

Nothing stated here rests on a forum thread or an article with no name attached to it. Where a point simply cannot be pinned down, the page admits as much instead of papering over it.

SmartPulseHome Independent reference

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