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How many and where?


Always put smoke alarms where you will be able to hear them throughout the home, particularly when you are asleep or when doors are closed. If your home has only one floor, fit the alarm between the living area and bedrooms.  If your home has more than one floor, we at S W Bishop Electrical always recommend fitting one alarm at the bottom of the staircase and further alarms on each landing.


Fit smoke alarms on the ceiling, as near as possible to the centre of the room, hallway or landing and position them at least 30cm (12 inches) away from any wall or light fitting. Make sure you can reach your smoke alarm easily to test it each week and avoid fitting it directly over a staircase.  Follow the manufacturers' instructions on how to fit your smoke alarm and change the battery.


Don’t fit your smoke alarm in or near to the kitchen or bathroom as it could be set off accidentally by cooking fumes and steam or in a garage where it could be set off accidentally by exhaust fumes. Never fit it on damp or dusty surfaces or false ceilings as there is a risk it will fall.


Leave that battery where it is!


At S W Bishop Electrical, we know how irritating it is when, every time you fry a sausage or roast a chicken, the alarm is triggered. Please don’t just remove the battery!  It may just be case of moving it a few metres.  Steam from baths and showers, cigarette smoke and gas or electric bar fires can also trigger alarms.


How often should you check your smoke alarm?


Once a week: Test your smoke alarm each week by pressing the test button on the alarm.


Every six months: Every six months you should open the case and gently vacuum the inside to remove dust from the sensor. If the smoke alarm doesn’t open, vacuum through the holes.


Once a year: Change the battery every year (unless it is a ten year alarm) or if the low battery warning sounds (an intermittent, very irritating bleep). If this sounds like a bit of a chore, you can now buy smoke alarms fitted with sealed 10 year batteries.  They are more expensive but well worth the money if you think an annual battery change may slip your mind.


Every ten years: It is also best to replace smoke alarms with completely new units after ten years.






At S W Bishop Electrical we recommend you set weekly, six monthly and yearly reminders on your mobile phone to remind you of the above. London Fire Brigade will visit your home and give you safety advice and where appropriate fit a smoke alarm for free.  Click here for details.


Smoke Alarms

What are the main types of smoke alarm?


Standard battery alarms: An 'ionisation battery alarm' is the cheapest and most basic smoke alarm available.  An 'optical battery alarm' is a little more expensive (see descriptions of both below). Both run off 9 volt batteries.


Mains-powered smoke alarms: These are powered by your home's electricity supply and need to be installed by a qualified electrician.  Here at S W Bishop Electrical, we recommend that you choose mains-powered smoke alarms with an internal backup battery. Some of these need replacing every year or so, others have re-chargeable lithium backup batteries that will last the full ten years of the smoke alarm’s life.


Linked or interconnecting alarms: If you have a large home or need a smoke alarm fitted in a commercial building, here at S W Bishop Electrical we recommend a linked or interconnecting alarm. When one alarm detects a fire they all go off together alerting people who may not have heard the original alarm. These alarms can be linked up to more complicated systems such as triggering water sprays or unlocking electric doors for quick exits.


What are the most popular models and how much do they cost?


Ionisation smoke alarms: These are the cheapest, starting at about £5.00 and most readily available smoke alarms.  They are sensitive to fiercely burning fires such as chip-pan fires. Ionisation alarms will detect flaming fires before the smoke gets too thick.


Optical smoke alarms: These are also known as photoelectric and are more expensive. They start at about £7.50 and detect fire with a small light beam within a chamber. These are most suitable for rooms with soft furnishings such as bedrooms, lounges as they are more effective at detecting slow burning fires such as smouldering foam filled furniture or overheated wiring. Optical smoke alarms are less likely to give false alarms from burnt toast.


Heat alarms: These detect excessive temperatures in a kitchen or garage. Some heat detectors also detect an unusual speed of temperature rise. These alarms are the answer to false alarms in your kitchen or garage. They are not suitable for the hall or the rest of the house. They start at about £25.00


Whichever model you choose, here at S W Bishop Electrical we recommend you should make sure that it meets British Standard BS EN 14604 and ideally also carries the British Standard Kitemark or LPCB ‘Horseshoe’ mark. The Code of practice for the design, installation and maintenance of detection and fire alarm systems in dwellings is BS 5839-6:2019




As you can see, it’s a smoke alarm jungle out there but I hope I have made things a bit clearer.  If you have any questions at all, please give me a call as I’m always happy to give advice over the phone.  Or you can make an appointment for a free quote for installation or a free assessment of your existing smoke alarms.  


Remember – any alarm is better than no alarm.


What is a smoke alarm?


A smoke alarm, (or smoke detector) is a small device fitted to the ceiling and is able to detect fires in their earliest stages and sound a loud warning alarm. This alarm can give you those precious few minutes of warning time which will help get you and your family out safely.