FireAngel FA3820 Carbon Monoxide Alarm Review

10 Year Lifetime Battery


When we think of home security most of us will automatically start thinking of burglar alarms, better window and door locks, security cameras etc., pretty much anything that secures our homes to keep thieves and intruders out. But home security is so much more than that. Yes, there are a plethora of products to keep your home and belongings secure from theft, but home security also involves protecting your home and the people within it in the event of fire with smoke alarms but also from the silent killer Carbon Monoxide (CO).

Carbon Monoxide is a very poisonous gas, one that you can’t see, taste or even smell. As it is so dangerous and can have devasting effects within our homes and garages, everyone should have at least one Cardon Monoxide detector alarm fitted within their home. Breathing in Carbon Monoxide can be lethal in enclosed spaces and can result in CO poisoning, illness or in some cases death. It’s created in our homes when the fuel in products, such as boilers, fires and ovens does not burn completely. Regular servicing of these products can reduce the risk of CO being present, but it cannot completely remove the risk. This shows how important having a CO alarm in the home is, and it is something that a lot of people forget to install.

FireAngel are a well-known and respected brand of fire safety products for the home with smoke alarms, carbon monoxide alarms and heat alarms. We were sent their FA3820 Carbon Monoxide Alarm to test out and review.

The FireAngel FA3820 Carbon Monoxide Alarm is a small device for the early detection and protection against carbon monoxide in the home. It is a sealed unit (you cannot replace the battery) powered by a 10 year sealed lithium battery and is certified for use in your home or whilst travelling. Whilst it does what other CO alarms do and detects dangerous levels of carbon monoxide within the home and sounds an alarm, it also has another excellent feature that most other alarms don’t have – using the latest sensor technology it features an early warning indictor, a pre-alarm warning which encourages ventilation of your property when low levels of carbon monoxide are detected.


  • 10 Years Lifespan
  • 10 Year Sealed Lithium Battery
  • 5 Year Warranty
  • Designed for Wall Mounting or Free Standing Installation (rawl plugs and screws are not supplied)
  • Certified for the home, caravans, motor homes, and boat use
  • Loud 85dB audible alarm activates when CO level reaches 50ppm
  • ‘Pre-alarm’ warning encourages ventilation of property when low levels of CO are detected
  • Kitemarked to BS EN 50291-1: 2018 (domestic use) and BS EN 50291-2: 2019 (camping / caravans / boats)
  • CE marked and UKCA marked
  • Low volume test function (Single press – self-test at a reduced volume / Double press – self-test at full alarm volume)
  • Silence low battery / end of life warnings with the Sleep Easy function for up to 8 hours
  • Simple activation with the removal of the disabling tab
  • Indicates previous alarm activation with memory function
  • Dimensions (HxWxD): 67 x 125 x 33mm
  • This alarm is also suitable for both the Welsh and Scottish updated 2022 legislation

The FireAngel Carbon Monoxide Alarm is an unobtrusive small white box that once installed you can mostly forget about (except for regularly testing). It can be wall mounted or free-standing and should be placed in a room with any fuel-burning appliance (boiler, oven, gas fire or wood-burning stove) – if you have more than one room with a fuel-burning appliance then ideally you should place a CO alarm in each one.

Installation is quick and simple, just pull the disabling tab out of the bottom of the device (don’t throw this away) and wait for the LED to turn green (can take up to 1 minute). Once the alarm is activated by removing the tab the battery should last up to 10 years. Test the alarm by pressing the TEST button (press once for a self-test at a reduced volume / press twice for a self-test at full alarm volume). Once the alarm is confirmed as working you can now site it where needed – for example, in the kitchen. Place the alarm between 1-3 meters away from the source (e.g. boiler) and on the same side of the room as the source (if wall mounting, place 15cm away from the ceiling, higher than doors and windows). If you are wall mounting, you will need to purchase suitable rawl plugs and screws for your walls as these are not supplied.

With the alarm installed and working it should detect any carbon monoxide in the room. Hopefully it will never be needed and will sit there silently but if carbon monoxide is detected in the air a very loud alarm will sound to warn you to take action. In the event of the alarm sounding never ignore it, ventilate the room by opening doors and windows, turn off the appliances if possible and leave the property. Do not enter the property until the alarm has stopped – this can take up to 10 minutes depending on the levels detected. Do not use the appliances again until they have been checked by an expert (for example, ring your fuel supplier’s emergency number).

The FA3820 Carbon Monoxide Alarm also features an early-warning indicator when low levels of carbon monoxide are detected, it has a different sound and flashing LED. This allows you to ventilate the room and get any appliances checked before a bigger problem can occur.

I’ve already mentioned that this is a sealed unit. It has a 10 year battery life and will need replacing once the battery is depleted. It will beep once per minute when the battery is dying, and this means that you have 30 days to replace the alarm. Once it is no longer detecting CO because of low battery levels it will emit 3 rapid beeps per minute and needs replacing immediately. As constant beeping will become annoying, especially at night when you want to sleep, the alarm is equipped with a Sleep Easy Silence feature that allows you to silence the alarm for 12 hours at night (for a maximum of 10 times), allowing you plenty of time to replace the alarm and not be annoyed by it whilst trying to sleep.

Overall, the FireAngel FA3820 Carbon Monoxide (CO) Alarm is a fantastic small and unobtrusive potentially life-saving battery powered device – every home should have one. It is extremely easy to activate and install, and is extremely loud at 85dB when activated, giving clear warning of a problem (it will also flash red, so you are visually aware as well). The early warning system is great for detecting issues before they become a very big problem. And the lower volume for testing purposes is brilliant (it is very loud at full volume).

Once installed, you can mostly forget about it – the only maintenance needed is to test the alarm once a month to make sure it is still working (testing couldn’t easier, just press the test button) and give it a quick vacuum every 3 months to remove any build-up of dust. You can’t clean it using any cleaners or solvents and never paint or cover it.

As it can be wall mounted or free-standing it is easy to use in any room and it is small and portable so that it can used in caravans, motor homes, boats, hotel rooms etc.

With a retail price of around £30 it is excellent value, with a 10 year battery it works out at just £3 per year (25p per month) – that is nothing to be able to protect your family from a silent, dangerous and potentially deadly gas (exposure to CO can result in mild symptoms including headache and vomiting to more extreme symptoms from prolonged exposure including unconsciousness, convulsions and even death – information on symptoms can be found on the NHS website).

The FireAngel FA3820 Carbon Monoxide alarm is an excellent quality CO alarm with intelligent sensing technology that results in audio and visual warnings to help protect you, your family and your home from a silent killer. It is so easy to use and maintain and is an easy way to help protect yourself and your family from something you can’t see or smell, something that can have horrible consequences.

Every home needs a carbon monoxide detector (and smoke alarms), and we can recommend the FireAngel alarm – the build quality is good, the alarm is very loud, the flashing LED notifications are very noticeable. Obviously we haven’t tested it by leaking CO into the room, but it has BSI Kitemark approval so has been tested by independent experts, so we are very confident that it will detect CO levels in the event of a faulty appliance.

When you are taking a look at your home security, don’t forget the smoke and CO alarms, they could prevent you from becoming ill and even save your life! And remember to get things like boilers and flues checked regularly with an annual gas safety check.

Rating: 5/5

RRP: £29.99

For more information, visit Also available to buy from Amazon here.

DISCLOSURE: We received this product for free for the purpose of writing an honest and impartial review. All thoughts and opinions are our own. This review uses an affiliate link which we may receive a small commission from if you purchase through the link.


Please enter your comment!
Please enter your name here