These contain a very small amount of radioactive material, which reacts to particles emitted in a fire and sets off the alarm. Ionisation alarms are best at detecting fast-flaming fires that don't emit much visible smoke. But many house fires tend to be smoky and smouldering long before they flare into flame, and ionisation alarms aren't as quick at detecting these. They can also be prone to nuisance alarms from cooking and steam, so shouldn't be located near your kitchen or bathroom.
These contain a photo cell and a light beam shining away from the cell. When smoke enters the test chamber, some of the light is scattered by the smoke particles and hits the cell, triggering the alarm. Photoelectric alarms are best at detecting smoky and smouldering fires, which is a common type of house fire. Dust or insects entering the unit can cause false alarms, so they have to be cleaned occasionally. These contain both an ionisation sensor and a photoelectric sensor, and so they get the best and worst features of both types.
They can be a good option but as with any ionisation alarm, don't install them near a kitchen or bathroom. Even if you have one of these specialised alarms, you should always have standard smoke alarms as well. Photoelectric alarms are the best type for homes, as shown by CHOICE tests and as recommended by most fire authorities. Photoelectric smoke alarms are usually much faster at detecting smoke from smouldering synthetic material than ionisation alarms.
In a typical house fire, burning material smoulders and smokes for a long time possibly a few hours before flaring into flames. It's crucial to detect the fire early in the smouldering phase so you can deal with the fire or escape the house; the longer the fire goes on, the more smoke can fill the home and become an inhalation and visibility hazard.
Studies have shown that photoelectric alarms typically respond to smoky fires within about three to five minutes. Ionisation alarms can take much longer — up to 20 minutes or more — by which time escape can be much more difficult.
CHOICE tests have shown that some ionisation alarms can respond quickly to smouldering fires, including smouldering synthetic material such as polyurethane foam, though generally photoelectric alarms outperform them in this situation. For example, Google said it developed a Steam Check feature, which ensures the alarm knows the difference between steam and smoke. This feature was developed from a combination of conventional lab testing and real data from the home.
UK smoke alarms are mostly likely to sound on pancake day, according to Google. Heat thermal alarms detect heat hot air instead of smoke. The alarm is triggered when the temperature within the sensor chamber reaches over 58 degrees Celsius — generally when a fire is well established.
But they are slower to respond than smoke alarms. If you buy a battery-powered smoke alarm rather than a mains-powered one , you'll need to decide whether you want one with a replaceable 9-volt battery, or a 'long-life' or year battery.
The latter are pricier when you buy for the first time, but you won't have to factor in the expense of replacement battery costs. You should replace a 9-volt battery in your smoke alarm whenever you need to, or at least annually. Now find the perfect smoke alarm for you by checking out our round-up of the best smoke alarms.
Test score. Which smoke alarm should you buy - ionisation, optical or heat alarm? Find out how to choose the best smoke alarm for your home. MS Matt Stevens. In this article How much do you need to spend to buy a good smoke alarm? The color-changing LED, along with the verbal commands and smartphone notifications, made the Nest Protect fun to test out and operate.
My first aerosol test activated its "heads-up" function, which issued a verbal warning that it detected a small amount of smoke. This would be a convenient feature if the smoke was due to burning toast or another non-emergency — especially for anyone who might get overwhelmed by loud noises. By giving you the chance to resolve the problem before the smoke levels rise, you can prevent the unit from going into full-blown alarm mode.
My second aerosol spray was enough for the Nest Protect to assume there was an actual fire, and it sounded its alarm immediately. You can even silence the alarm from your smartphone, although it doesn't allow for this if the smoke is too heavy. The Nest Protect is a hardwired unit, so installation was a bit more elaborate than the other smoke detectors I tested. This will involve working with and reconnecting electrical wiring, so if you're uncomfortable around that type of thing, you may want to hire a professional.
It took me about 15 minutes to remove the previous unit and connect this one. The instructions walked me through every step of the process, and the included hardware was effective and easy to use. It also took me about 15 minutes to connect the Nest Protect to my home's Wi-Fi network due to connection issues. If your home Wi-Fi goes down like in the event of a power outage, the Nest Protect will continue to work just fine — you just won't get any notifications on your phone.
The three AA batteries will ensure the Nest Protect continues to work during a power outage. The X-Sense SD01 has a nice, solid feel to it, and the large LED escape light gives it a professional look, like something you would see in a commercial building. This light automatically turns on when the alarm is activated, and it not only alerts you about the presence of smoke but can also help to illuminate a darkened room. This is an especially important feature as more than half of home fire-related deaths occur between 11 p.
This light would also be extremely valuable in the event of a power outage, a feature that Andler praised and why he endorses the X-Sense SD01 so strongly. This unit responded well to my tests and activated after two aerosol sprays. I made sure to perform one of my tests at night to best observe the escape light and was very impressed with how bright it was. The light, the loud alarm, and a flashing red secondary LED would be effective in the case of a real emergency.
These high-visibility features also make the X-Sense SD01 a great option for hallways and stairwells as long as you have one or two on the ceiling as well. The X-Sense SD01 has a built-in, year battery, so it will last for the life of the unit, and then you'll need to purchase an entirely new alarm. It's also designed to constantly auto-check itself to make sure its batteries are in working order. In the event of an issue, the secondary LED will turn yellow, alerting you that something is wrong.
The X-Sense SD01 uses a photoelectric sensor, which works with the air-flow design of the casing to better detect a variety of fire types. The sensor also analyzes smoke three times before activating the alarm, which minimizes nuisance alarms.
Installing the X-Sense SD01 was a breeze, just like the other X-Sense models, and I had the mounting plate installed and the unit in place within a couple of minutes. Pros: Has both photosensitive and ionization sensors, has safety features suitable for landlords.
The First Alert SA features both photosensitive and ionization sensors, which is likely the reason why it was the only unit that activated its alarm after a single aerosol spray test. Although this high sensitivity sounds good on paper, it can also be the cause of frequent nuisance alarms. These alarms, combined with the removable AA batteries, greatly increase the odds that someone will remove the batteries or the alarm itself.
I didn't experience any issues installing the First Alert SA It uses red wall anchors, which aren't ideal if you want to move the unit to a different location in the room. It also has optional locking features to discourage unauthorized battery or alarm removal. There are two pins you can insert into the sides of the unit or by the battery compartment that expand once they're in place to prevent anyone from taking down the smoke detector or removing its batteries.
You "unlock" the unit with a flathead screwdriver to depress the pin's teeth. This is a good feature for landlords or anyone else placing the unit who won't be there to monitor it. The First Alert SA's design makes it feel more functional and less clunky. It does lack the polished appeal of the X-Sense models, though it shouldn't be a big factor compared with safety and effectiveness.
Andler describes this as "a standard smoke detector at a good cost. Pros: Small size is easy to install, easy to find silence button in the dark, covers large areas. Even though the X-Sense Wireless Interconnected smoke detectors are smaller and lighter than typical ones, they still meet UL standards. They also beeped at the same db level as every other model tested. Their red alert lights were easy to see, and because of their side-mounted position, they reflected off the ceiling to increase visibility.
Because they are interconnected, all the units will sound even if only one detects smoke, so you'll be notified regardless of where you are in your home when a fire breaks out. They performed effectively in every test I did and were all relatively sensitive, responding within two aerosol sprays. Since the silence button is also the alert light, it was easy to quickly find the button to silence the unit, even in low light. Each unit was interconnected right out of the box, so there was no additional setup necessary.
You can add up to 24 units to the network, but every new set will need to be manually connected to the rest. You should also have a carbon monoxide detector on each living level, outside each sleeping area, in the basement, and near not inside an attached garage. Use the illustration below as a guide to where you need detectors, and tally up the number of smoke and carbon monoxide detectors you need to buy. Keep in mind that your home might need more or fewer detectors, depending on its size and number of rooms.
Check Local Regulations Before you shop, check regulations in your area. Also, some insurance companies offer a discount for homes with smoke detectors. Battery-only detectors are the simplest to install, and they work during a power failure. Some models use removable batteries that require annual replacement, while others use sealed lithium batteries that last the life of the detector.
Plug-in detectors are also available, but electric outlets are typically located low on the wall, while the optimal placement for the detector is on or near the ceiling. But if you decide to outfit your home with them, we recommend also installing additional dual-sensor smoke detectors. Smart detectors, whether hardwired or battery-powered, will also interconnect with other detectors of the same model. Another option is the Roost Smart Battery , which replaces the 9-volt battery in smoke and CO detectors that use them.
It adds WiFi, smartphone alerts, and in-app hushing for battery-powered models only to existing detectors. You should also look for the date of manufacture printed on the back of the detectors. Devices lose their sensitivity over time, so the fresher, the better.
As a rule of thumb, replace carbon monoxide detectors every five years and smoke detectors every 10 years. UL has also announced updates to its standards, which will require all manufacturers to make smoke detectors that can distinguish between smoldering fires and cooking smoke by the end of June The Truth About Interconnected Detectors You can interconnect some smoke and carbon monoxide detectors so that all units in the house sound an alarm when any single one is triggered. Some newer homes may have wiring already in place to link the detectors.
In a home without such wiring, you can buy detectors that interconnect wirelessly. These interconnected smoke and carbon monoxide detectors are an important safety feature in a home with multiple levels, although standalone detectors may be adequate for a small, single-level home.
While interconnected alarms can make your home safer, they have some limitations. In many cases interconnected alarms can interconnect only with models made by the same brand. Despite the limitations, we recommend using interconnected detectors. They can make your home much safer by alerting you to danger before the fire or CO spreads throughout your home.
Roux adds that interconnected alarms whether hardwired or wireless are also becoming a requirement in many states when you try to sell your home. Consider Voice Alerts Children tend to sleep more deeply than adults and might not awaken to a conventional alarm. Consider Your Security System You can incorporate some smoke and carbon monoxide detectors into a security system that sounds an alarm outside and inside the house. Such systems may also have a monitoring service that can notify the police or fire department, or even call your cell phone.
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