Smoke Detectros: Types, Uses and Benefits
Smoke detectors can be found in both residential and commercial buildings across the UK and they are essential to the fire safety of your property. Below we’ll discuss the different smoke detector types, how they work and which ones are better.
What is a smoke detector?
A smoke detector is an important part of your fire safety equipment. It’s a device that is usually attached to the ceiling, which detects smoke as a sign of fire. Home smoke detectors are also referred to as smoke alarms because as soon as they detect smoke, they start flashing and making a loud noise to alert the occupants of the possible fire danger. In a commercial fire alarm system, the smoke detector sends out an alert to the fire alarm control panel, which then switches on specific alarms and may even initiate an evacuation procedure.
Sensitive smoke detectors can also be installed in no-smoking areas to deter people from breaking the restrictions. For example, this application of smoke detectors is often used in trains and planes.
Types of smoke detectors
There are two main types of smoke detectors: optical smoke detectors and ionisation smoke detectors. However, a smoke detector isn’t necessarily either one or the other. Depending on the design, some detectors may use both methods of detection. Those are called dual sensor smoke alarms.
Optical smoke detectors
Optical smoke detectors (also called photoelectric detectors) are faster to detect fires at their smouldering stage than ionisation smoke detectors. Their mechanism usually contains a source of light, a photoelectric receiver and a lens. There are various designs of optical smoke detectors but they all work on the principle of detecting changes in the light source due to smoke.
Optical beam alarms will detect any reduction of the light intensity due to obstruction by smoke. Alternatively, there are chamber photoelectric detectors, which are designed so that the light reaches the photoelectric receiver only if it’s scattered by particles present in the chamber. This type of optical smoke alarm is prone to false alarms because not only smoke but also dust particles can trigger the alarm.
Ionisation smoke detectors
Ionisation smoke detectors use the physical process of ionisation to detect smoke particles. They are less effective than optical smoke detectors when it comes to smouldering fires but they are more effective in detecting the flames of a burning fire.
The basic mechanism of ionisation smoke detectors is made up of two chambers, a radioactive source (usually americium-241) used for ionisation, an electric circuit and an alarm. One of the chambers allows airflow from the room whereas the other (the reference chamber) is completely isolated from external particles. The radioactive source ionises the molecules in both chambers and as the ions are electrically charged, an electrical current is produced. If fire particles enter the chamber, some of the ions will bind to them, reducing the electric current. When that happens, an electronic circuit within the detectors picks up on the difference between the two chambers and sounds the alarm.
Aspirating smoke detectors
Outside of the classic smoke detector types, there are the more complex aspirating smoke detector (ASD) systems. They include a network of pipes that take samples of air from various rooms and detect smoke using the optical detection method.
What makes aspirating smoke detectors a more advanced solution is that they use a filtration system which prevents all other particles but smoke particles from entering, by which they remove any risk of false fire alarms caused by dust. Another major benefit is that the sensitivity of the ASD detectors can be programmed to be as high or as low as you like. They can be thousands of times more sensitive than a traditional smoke detector or completely the opposite, depending on what they will be used for.
CO2 detectors are not smoke detectors as they are not triggered by the presence of smoke alone. They measure the CO2 levels in the air and sound the alarm if dangerously high levels, typically associated with fire, are detected. They detect fires much faster than any smoke detector and are immune to false alarms caused by dust, which makes them perfect for dusty or dirty areas.
Wired smoke detectors vs wireless smoke detectors
Smoke detectors also vary based on their power source. If you would like to have a smoke detector installed, you will have to make a choice between wired (mains) smoke detectors and wireless (battery-powered) smoke detectors.
Wired smoke detectors are plugged directly into the mains system, which means they are harder to install as additional wiring may be required. However, mains-powered smoke detectors are more reliable because as long as the electricity is working, they will as well. Plus, some have a back-up power supply in case of an emergency. Therefore, if you don’t want to have to worry about changing the battery of your smoke detector regularly, a hardwired smoke detector might be a better choice for you.
Wireless smoke detectors are the more widely used model nowadays. This is because they are battery-powered which makes them much cheaper and easier to install. As long as you keep the battery working, the wireless smoke detector will do its job. If you forget to change the battery and it starts to die, the detector will alert you by making a persistent beeping noise.
Both wired and wireless smoke detectors have an average lifespan of 10 years and need to be inspected regularly to make sure they work properly. Picking one over the other is a personal choice and no solution is better than the other.
Heat detectors vs Smoke detectors
People often wonder about the difference between heat detectors and smoke detectors, whether you need both or if a smoke detector can be replaced by a heat detector. The answer is that they are different, it’s always better to have both but if you have to choose the smoke detector is the better option.
The difference between heat and smoke detectors is that heat detectors are designed to detect changes in temperature caused by fire and sound an alarm, whereas smoke detectors can pick up fires before they start flaming aggressively based on the smoke produced.
The main purpose of heat detectors is to protect a property from fire damage and they can be set up to trigger fire sprinklers upon a significant heat increase. Smoke detectors, on the other hand, are more suitable when your aim is to protect the people at the property, as they can alert them to smoke before the fire has become too dangerous, which allows for quicker evacuation.
Smoke detectors are also faster than heat detectors at identifying a fire. Some fires start with a prolonged period of smouldering where smoke is produced but complete combustion doesn’t occur until later, which means that the fire can spread before enough heat is generated to trigger the heat detector. This is why if you need to choose whether to have just a smoke detector or just a heat decor installed, the safer option is a smoke detector.
Where possible, having both installed is the optimal solution, as it offers double the protection and you can never be too cautious when it comes to fire safety.
Let’s round this guide on smoke detectors in the UK with a quick FAQ section that answers your most common questions about smoke detectors!
What type of smoke detector is best?
Ionisation smoke detectors are better for detecting flaming fires while optical smoke detectors are better at detecting smouldering fires. To ensure maximum security, you should have both or a combination smoke detector device.
Is it a legal requirement to have a smoke detector?
Yes, the UK fire safety standard mandates the installation of a smoke alarm on every storey of a building which is used either fully or partially as living accommodation.
Where should smoke detectors be located?
Smoke detectors should be installed as close to the centre of the ceiling as possible. If not, then they should be ideally at least 300mm away from the wall.
How often should I test my smoke detector?
The smoke detector should be tested at least once a month and the batteries should be replaced annually.
How to stop a smoke detector from beeping?
If there is no smoke but your smoke detector is beeping, then either the battery is dying or the smoke detector needs to be reset. To reset the smoke alarm, remove the battery and press the reset button for 15-20 seconds. If the beeping continues afterwards, then you should probably replace the battery.
Evacuator Alarms offer specialist fire safety equipment for construction sites, including wired and wireless fire alarm systems for maximum protection. We supply and install a large range of high-quality fire detectors for commercial use.