What causes “chirping” and false alarms in smoke alarms?

This post was written in 2016 and a more recent version exists. Please read our new guide to troubleshooting beeping smoke alarms.

hoovering-alarmIf your smoke or heat alarm is beeping or “chirping” in the middle of the night with no obvious reason, you may begin to see it as an annoyance rather than a life saving device.

False alarms and chirping are often alerting you of problems that require attention. There are a number of checks that can be done to help find the cause before seeking further help from the manufacturer or retailer. Below is a step-by-step guide to the possible causes and solutions for false alarms and chirping; however, always refer to the manufacturer’s instructions for your exact smoke or heat alarm model. Additional care should be taken with mains powered alarms, as interference with the alarm can cause electrocution.

1) Are you using the correct type of smoke alarm?

There are three main types of domestic alarms available on the market:

Ionisation Smoke Alarms – Slightly quicker at detecting fast flaming fires than other technologies but usually only installed in upstairs landing areas. If installed near a kitchen, where the occasional toast might get burned, ionisation alarms can cause false alarms. The installation of this alarm near sources of smoke is one of the key reasons for false alarms in daytime.

Optical Smoke Alarms – Slightly quicker at detecting slow smouldering fires that can originate from upholstery type materials and over-heated wiring. Suitable to be installed in bedrooms, living rooms and downstairs hallways. These are fairly ‘toast-proof’ and can be installed near kitchens (not in kitchens, though).

Heat Alarms – Activate when the temperature inside the room reaches a certain trigger level or if the heat in a room rises very quickly. These are ideal in kitchens and garages, as they do not get triggered by fumes. Please note that a heat alarm only covers a small area, so larger kitchens will require several heat alarms.

All types of alarm will sound in the event of a fire; however, understanding more about each sensor technology helps you to select units that are least likely to cause false alarms. Alarms placed in the wrong location will on the other hand cause false alarms, eg if you have a smoke alarm located in the hallway and this sounds each time you use the toaster or boil vegetables, it is likely that you have an ionisation smoke alarm installed rather than an optical.

2) Is the alarm in the optimum position?

The user manual for your smoke or heat alarm will provide advice on where to avoid positioning your alarm on the ceiling. Below are some examples of locations to avoid placing your smoke or heat alarm:

  • Near fluorescent lights – as electronic “noise” can cause false alarms
  • In front of air supply ducts for heating or air conditioning, or near ceiling fans
  • Directly above cookers/toasters/kettles (heat alarm) – although heat alarms are designed not to cause false alarms from cooking fumes, they should not be installed directly above cooking appliances
  • Within 0.9m (3ft) of the door to a bathroom or shower room (smoke alarm) – steam can cause false alarms

3) Is there dust and/or insects inside the alarm?

Smoke alarms contain a sensor which is used to detect a fire. Over time, dust can build up or small insects/flies can crawl inside the unit, obstruct the sensor and eventually cause false alarms. Cleaning your alarm helps to remove anything that could be blocking the sensor. Wipe the outside of the alarm with a damp cloth, then using a vacuum nozzle or a hair dryer (set on cold), to suck or blow through the openings of the alarm.

4) Have you been decorating nearby?

If decorating, especially sanding, has recently taken place, dust particles or paint fumes could have entered the sensor chamber, causing damage to the unit and therefore causing false alarms. It is recommended to temporarily cover the alarm whilst decorating. Some alarms are supplied with a protective cover, so keep hold of this after installation for any future use. If you suspect decorating may have affected your alarm, try cleaning the unit as described above.

5) Is the temperature causing the alarm to beep?

Smoke alarms have an optimum operating temperature and it is important to ensure that your alarm is not subjected to temperatures above or below these thresholds. Typically, the operating temperature for a smoke alarm is between 0 ˚C to +40 ˚C. If the alarm is positioned where it may experience blasts of hot or cold air e.g. close to a front door, or the ambient room temperature is not constant e.g. in attics, this is when false alarms can occur. It may be necessary to reposition your alarm.

6) Is the alarm at the end of its life?

Each smoke and heat alarm should have a sticker located on the edge or the back of the unit indicating a replace-by date. This is usually ten years after manufacture. If your alarm starts chirping or regularly sounds falsely, it could mean that the alarm is close to, or has reached the end of its life. Check the date to see if the alarm is due to be replaced.

7) Is there a problem with the mains supply?

Mains powered smoke alarms can usually be identified by two LEDs located on the face of the unit. One LED flashes red approximately once a minute to indicate that the unit is operating correctly. The second LED should be constantly green to indicate that mains power is present. If the green LED is not present, this could mean that there is an issue with the mains power getting to the alarm. If needed, advice should be obtained by a qualified electrician.

8) Is the battery running low?

Chirping every 30-40 seconds is generally an indication that the battery is running low. If your smoke or heat alarm has a replaceable battery, try replacing the battery with a brand new one. It is recommended to change the batteries in your smoke and heat alarms every 12 months. Changing your battery before it runs low helps to overcome the annoying chirps at night. Change the batteries when the clocks are changed forward or register for a free email reminder service.

Many smoke and heat alarms are now fitted with a sealed lithium battery, designed to last the life of the alarm. These batteries are not accessible for replacement and so if your alarm starts chirping but has a non-replaceable battery, the alarm may have reached the end of its life. Batteries running low apply to both solely battery powered alarms as well as mains powered units with a back-up battery.

9) Is there another alarm nearby?

If you have tried all the above and you can still hear chirping, the final check is to see if there is another alarm or device within the same area that could be causing the chirp. It is easy to associate chirping with smoke and heat alarms and forget that other devices e.g. carbon monoxide detectors could also contain a battery that is running low.

Safelincs are happy to provide information regarding your smoke and heat alarms. For more information, you can also visit our Smoke Alarm Help Guides page, or contact our customer services team.

Which type of smoke alarm should I use?

Smoke alarms are the most essential components in any fire safety strategy, whether in commercial or domestic properties.

There is a wide range of smoke alarm models available designed to suit various circumstances. It is therefore important to ensure that you purchase the correct model for your requirements, in order to ensure your smoke alarms operate as efficiently as possible.

Below is a summary of the various smoke alarm models featured on our website:

Optical smoke alarms are suitable for general use and are especially suitable for detecting smouldering fires caused for example by smouldering soft furnishings. They are also not too sensitive to false alarms from burnt toast, making them ideal in hallways (near kitchens), living rooms and bedrooms.

Ionisation smoke alarms are able to detect the change in the behaviour of the air in case of a fire. Fast flaming fires, such as burning waste paper baskets, are easily detected by ionisation smoke alarms and we recommend ionisation smoke alarms for use in offices or on landings. Please note that ionisation smoke alarms contain a small amount of radio-activity. If you wish to avoid this, choose optical smoke alarms instead.

Heat alarms are designed to detect the increase of temperature caused by a fire and do not cause false alarms. They are especially useful in dusty or smoky areas, such as kitchen and garages. They do, however, not cover very large areas, so cannot really be used for larger parts of a building.

Multi-sensor alarms combine the features of optical and heat alarms, resulting in rapid fire detection and a reduced risk of false alarms. They are suitable for living rooms, bedrooms, hallways and landings but should not be used in kitchens.

If you require further advice on which smoke alarm design is suitable for you, please don’t hesitate to contact us today. We also publish a guide on the different smoke alarm technologies.

For warehouse areas and industrial properties we offer more fire detection technologies and central alarm panle systems.

How to protect a kitchen with heat detectors

Kitchens produce great amounts of steam and cooking smoke and ordinary smoke alarms are not able to cope with these confusing signals. An ionisation smoke alarm or even an optical smoke alarm would quickly be set off when a kitchen is being used. At the same time fires regularly start in the kitchen, so rapid fire detection is important.

Luckily, there is an easy solution available. Heat alarms or heat detectors work by detecting either rapidly rising temperatures or trigger when a certain temperature is reached. Heat detectors do not get set off by steam or smoke or the normal cooking tempreatures. The thermistor in the heat detector head only detects the temperature changes mentioned above and ignores all other influences.

To notify the rest of the house of a fire in the kitchen you do not need to rely solely on the siren in the heat detector. You can interconnect the heat detectors with other smoke alarms in the house either with wire or through radio-frequency. The latter avoids you having to lay cables between alarms.

Heat detectors are also installed in garages and other areas where smoke or gases are present (with exception of bathrooms).

More information about the workings of heat detectors and other smoke alarms can be found in our smoke alarm guide.

Chip pans cause fires, don’t be caught out!

After a good night out with friends in the pub there is nothing nicer than to get back home and finish the evening off with a midnight snack. For many people it is the last snack that they will prepare. Chip pan fires are the cause of many house fire deaths, many of them occurring as a result of the midnight munchies after a night out.

A chip pan that is left unattended can burst into flames. Many people putting the chip pan on after a night out, go and sit down while it is heating up; they fall asleep and without them being aware the chip pan bursts into flames. If a heat or smoke alarm is fitted in or near the kitchen, the occupant will be alerted to the fire and will have the time to evacuate the building and call the fire brigade.

Where there is no smoke or heat alarms fitted the story has a different ending. Unlike the perception that many people have that they will wake from the smell of smoke, the smoke overcomes them and they die of smoke inhalation before the flames reach them. Smoke is toxic and after only a few breaths you can be rendered unconscious, not giving you enough time to escape to safety.

By following two very simple safety steps you will reduced the risk of dying in a house fire.

1) Ensure that you have working smoke alarms fitted in your home.

2) Get a take-away after a night out rather than putting the chip pan on or put something in the microwave.

Here are some real life accounts from fire fighters who have attended fires caused by cooking after a night out where someone has died