The Purpose of Smoke Detectors
Smoke detectors save lives by alerting people to a fire. They’re a common part of many homes, and often required by law. Electrician Boca Raton will decide where to place your smoke detectors so that you and your family are as safe as possible. They can also carry out the installations and routine inspections.
Ionization-type smoke alarms use radioactive material in small amounts (that pose no health risk) to ionize air molecules between pairs of electrodes. When smoke enters the chamber, it disrupts the flow of electricity and sets off the alarm.
They Detect Smoke
Smoke detectors are designed to detect smoke, which is a sign of fire. They can sense the presence of smoldering smoke or flames, and they can also recognize some types of carbon monoxide. The best smoke detectors will provide enough warning that occupants can escape the home safely.
The earliest smoke detectors were developed in the late 1930s. Walter Jaegar, a Swiss physicist, was working on a sensor to detect poison gas when his device failed to register concentrations of gas. Frustrated, he lit a cigarette and noticed that the smoke particles moved the meter on his instrument. This discovery led to the modern smoke detector.
There are two main types of smoke detectors, ionization and photoelectric models. Both work by constantly running an ongoing process, and when smoke interrupts this process, the detector will sound its alarm.
Ionization models use a small amount of radioactive material to ionize the air in a chamber within the detector. This ionization creates an electrical current that flows between two electrically charged plates, which is detected by a sensor. When smoke enters this chamber, it absorbs alpha particles and disturbs the ionization process. This reduces the current and activates the alarm.
Photoelectric smoke detectors contain a light source and a sensor, and the light shines into the sensing chamber at an angle. When smoke enters the chamber, it scatters the light, reducing the intensity of the signal that hits the sensor and triggering an alarm. This type of detector is less prone to false alarms than ionization models, but it is not as effective at detecting smoldering fires that start with smoke and then quickly break into flames. Some smoke detectors are powered by a permanent AC current, while others use non-rechargeable lithium batteries. These batteries have a typical lifespan of ten years and should be replaced regularly. They are available at most hardware and home improvement stores. Some smoke detectors are also equipped with user-replaceable, 9-volt rechargeable backup batteries. These last longer than standard alkaline batteries and can be purchased at most grocery and drugstores.
They Detect Flames
Smoke detectors are designed to detect flames, but they can also detect smoke particles caused by a smoldering fire. The smoke particles are then able to trigger the alarm, which can help alert people of danger in time to get them out of the building. In some cases, they may even prevent a fire from spreading, preventing more damage and possible loss of life.
There are two basic types of smoke detectors: photoelectric and ionization. Ionization models use a radioisotope to ionize the air inside a chamber, which then allows current to flow between pairs of electrodes that make up an alarm circuit. When smoke enters the open chamber, it causes some of the ions to attach to the particles in the air, which then reduces the current flowing between the electrodes and triggers the alarm.
Photoelectric smoke detectors use a light source and a sensor to detect smoke. The light source emits a beam of invisible infrared radiation, and the sensor device is positioned at right angles to it. When the smoke particles in the chamber cross the path of the beam, they interrupt it and cause the light sensor to turn on. When the alarm is activated, it emits a high-pitched tone that warns people of danger.
Many manufacturers now offer hush features that allow smoke detectors to be silenced, either temporarily or permanently, without having to remove the battery. This can be useful in areas where smoke is commonly generated by cooking, smoking or dust. It is still a good idea to test the unit and replace the batteries periodically, as they have a typical lifespan of about 10 years. Those that are directly connected to a building's wiring usually have an emergency backup battery, typically a lithium cell that lasts about ten years, so they can continue to work in the event of a power outage. Some manufacturers also sell user-replaceable lithium batteries that have a longer lifespan, such as 15 to 20 years. These can be used in conjunction with the traditional rechargeable batteries to ensure proper operation of the system.
They Detect Carbon Monoxide
In a house fire, people often have less than three minutes to escape before the flames reach them. This is why smoke detectors are considered essential safety devices. In fact, they reduce the risk of death from house fires by up to 55%.
Smoke alarms use one of two methods to detect smoke or other hazardous substances: ionization or photoelectric. Ionization detectors work by creating an ion cloud inside their detection chamber that changes shape when smoke particulates interrupt it, causing the device to trigger its alarm. They are cheaper and more common in domestic applications but can be prone to false alarms from simple kitchen particulates or dust.
The photoelectric smoke detector has a light source that shines into a sensing chamber containing a light-sensitive element. The light is positioned so that the element cannot ordinarily "see" it. But when particles of smoke enter the chamber, they reflect off of them and interfere with the ray of light that is directed toward the sensor. This breaks the circuit, triggering the alarm. This type of detector is more effective at detecting smoldering fires that don't produce as much visible smoke as flames.
Carbon monoxide detectors use a different method of detection. Known as the silent killer, carbon monoxide is odorless, tasteless and colorless, making it hard to detect without a special detector. Carbon monoxide detectors can sense the gas through its chemical composition and sound their alarm when it reaches dangerously high levels, typically around 400 parts per million (ppm).
Some smoke and carbon monoxide detectors are combined into a single unit that combines both functions. These units are usually labeled as such, so look for a UL Certified label to ensure the detectors have passed all applicable safety tests. You can also get smart detectors that connect directly to a home security system, so when they go off, your entire security platform is triggered. They can also send notifications to your mobile device, ensuring you are always aware of what is happening in your home.
They Detect Heat
You only have about three minutes to escape a fire when it breaks out at home, according to the National Fire Protection Association (NFPA). That’s why smoke detectors are found in homes and businesses throughout the country. In addition to detecting smoke, heat and carbon monoxide they also alert occupants to dangerous conditions that might not be immediately obvious.
In fact, smoke detectors were first invented by a Swiss physicist named Walter Jaeger in the 1930s while he was working on a device to detect poison gasses that could be lethal in mines. His device didn’t work, but his failure did inspire him to come up with an alternative that could alert people quickly when there was a fire.
His innovation was a smoke detector with two electrically charged plates that ionized the air in the device’s chamber. The ions caused by the ionization process conducted a small current between the plates, and when smoke entered the chamber it knocked electrons off of the atoms in the air, diminishing the current flow and triggering the alarm circuit.
Ionization smoke detectors are still the most common variety in use, but they’re less responsive to slow-burning “smouldering” fires than photoelectric ones. They also have a higher rate of false alarms that are often caused by things like cooking or using the bathroom. However, a dual-sensor smoke/carbon monoxide detector is the best choice for most facilities as it offers more accurate detection and prevents thermal lag.
While some smoke detectors only detect heat, most of the models in use today are capable of both detecting smoke and hot gases. To accomplish this, they have a special type of sensor that’s capable of sensing both light and heat. The sensors are located in a different area in the device depending on whether it’s a photoelectric or ionization model, and they’re designed to sense changes in temperature rather than just light or dark.
Most commercial smoke detectors are photoelectric, but they can also be ionization models with an integrated photoelectric sensor or one that’s separate from a traditional light-emitting diode. Some of these units are capable of detecting both light and smoke, and others have a special feature called rate-of-rise compensation that avoids false alarms from cigarette or cooking fumes by compensating for the natural thermal rise caused by those sources.
Smoke detectors save lives by alerting people to a fire. They’re a common part of many homes, and often required by law. Electrician Boca Raton will decide where to place your smoke detectors so that you and your family are as safe as possible. They can also carry out the installations and routine inspections. Ionization-type…