Portable Smoke Detector
But how do smoke alarms work in the first place?
Smoke alarms detect particles in the air. They most commonly do this using two types of detection technologies.
First, there are ionization detectors. These use a small bit of safely shielded radioactive material that electrically charges, or ionizes, the air molecules between two metal plates. This produces a small electric current flowing from one plate to the other in the air. When particles enter the chamber, they attract the ions and carry them away, reducing the current. When the number of particles entering the chamber is enough to reduce that current below a certain amount, the device will register those particles as smoke and the alarm will sound. (And about that radioactive material? Most of its radiation is blocked inside the device, and even then, the radiation levels in the device are much lower than the natural background radiation to which we are exposed every day.Portable Smoke Detector
The other type of commonly used detection technology is called photoelectric. This technology works by detecting light that is reflected off particles from a light beam inside the sensing chamber. When no particles are present in the sensing chamber, the light from the beam does not strike the light detector, indicating all clear. When there are particles present and the amount of light registered by the light detector reaches a certain threshold level, the alarm sounds.
Smoke swirls around a white smoke detector on a ceiling.
Credit: Cytokine/Shutter stock
Both kinds of detectors can detect either slow-burning “smoldering” fires or fast-burning “flaming” fires, but each technology has its particular strengths. Ionization-based alarms tend to detect small black soot particles from flaming fires more quickly because they are produced in greater numbers and take away more current from between the plates. Photoelectric detectors tend to be more sensitive to particles that are larger in size and white or light-colored, and thus more reflective, like those emitted by smoldering fires.
Portable Smoke Detector
that people have both ionization and photoelectric units in their homes. And dual-sensor alarms that combine both technologies are also available.
As important as smoke alarms are for protecting your family and your property, many times they can be a nuisance. Smoke alarms near kitchens can detect the particles coming off your food as it cooks, even if you don’t burn it. Sometimes something as simple as turning on a toaster can set them off.
So as with many safety measures, smoke detectors have a trade-off. They can be made sensitive enough to detect almost any smoke. But if they did, they would detect the smoke you don’t want them to detect (such as from cooked food) and even other things such as dust. Less sensitive detectors would have fewer nuisance alarms, but in an actual fire, they may not go off in time to save lives or property. Or they may not give off a signal at all Portable Smoke Detector
Researchers are developing new tests and standards to make smoke alarms better at detecting the kinds of smoke we want them to detect and not the kinds we don’t, so we’re never tempted to disable the alarms and put ourselves in danger. As a result, the next generation of smoke detectors promises to cut down on the number of nuisance alarms while also signaling real fires more quickly. And with fire, time is everything when it comes to saving lives and property.
The detector adopts the special structure design and , has the rustproof, moth proof and
anti outside light interference feature etc
Alert and warn people stay far away from danger field when it detected smoke
Alarm test button
Easy to install
9 Volt battery included
Photoelectric sensor for early detection from all directions
Alarm Volume: 10 feet to 85 dB
Wireless Mode: Alarm smoke
A smoke detector is a device that senses smoke, typically as an indicator of fire. Smoke detectors are usually housed in plastic enclosures, typically shaped like a disk about 150 millimeters (6 in) in diameter and 25 millimeters (1 in) thick, but shape and size vary. Smoke can be detected either optically (photoelectric) or by physical process (ionization). Detectors may use one or both sensing methods. Sensitive alarms can be used to detect and deter smoking in banned areas. Smoke detectors in large commercial and industrial buildings are usually connected to a central fire alarm system.
Household smoke detectors, also known as smoke alarms, generally issue an audible or visual alarm from the detector itself or several detectors if there are multiple devices interlinked. Household smoke detectors range from individual battery-powered units to several interlinked units with battery backup. With interlinked units, if any unit detects smoke, alarms will trigger at all of the units. This happens even if household power has gone out.
Commercial smoke detectors issue a signal to a fire alarm control panel as part of a fire alarm system. Usually, an individual commercial smoke detector unit does not issue an alarm; some, however, do have built-in sounders.
The risk of dying in a residential fire is cut in half in houses with working smoke detectors. The US National Fire Protection Association reports 0.53 deaths per 100 fires in homes with working smoke detectors compared to 1.18 deaths without (2009–2013). However, some homes do not have any smoke alarms, and some homes do not have any working batteries in their smoke alarms
The first automatic electric fire alarm was patented in 1890 by Francis Robbins Upton, an associate of Thomas Edison. In 1902, George Portable Smoke Detector Andrew Darby patented the first European electrical heat detector in Birmingham, England. In the late 1930s, Swiss physicist Walter Jagger attempted to invent a sensor for poison gas. He expected the gas entering the sensor to bind to ionized air molecules and thereby alter an electric current in a circuit of the instrument. However, his device did not achieve its purpose as small concentrations of gas did not affect the sensor’s conductivity. Frustrated, Jaggeder lit a cigarette and was surprised to notice that a meter on the instrument had registered a drop in current. Unlike poison gas, the smoke particles from his cigarette were able to alter the circuit’s current. Jagger’s experiment was one of the developments that paved the way for the modern smoke detector. In 1939, Swiss physicist Ernst Meili devised an ionization chamber device capable of detecting combustible gases in mines. He also invented a cold cathode tube that could amplify the small signal generated by the detection mechanism so that it was strong enough to activate an alarm.
In 1951, ionization smoke detectors were first sold in the United States. In the following years, they were used only in major commercial and industrial facilities due to their large size and high cost. In 1955, simple “fire detectors” for homes were developed, which detected high temperatures. In 1963, The United States Atomic Energy Commission (USAGE) granted the first license to distribute smoke detectors that used radioactive material. In 1965, the first low-cost smoke detector for domestic use was developed by Duane D. Pears all and Stanley Bennett Peterson. It was an individual, replaceable, battery-powered unit that could be easily installed. The “Smoke Gard 700″ was beehive-shaped, fire-resistant, and made of steel. The company began mass-producing these units in 1975. Studies in the 1960s determined that smoke detectors respond to fires much faster than heat detectors.
The first single-station smoke detector was invented in 1970 and was brought out the next year. It was an ionization detector powered by a single 9-volt battery. It cost about US$125 (equivalent to $941.95 in 2022) and sold at a rate of a few hundred thousand units per year. Several developments in smoke detector technology occurred between 1971 and 1976, including the replacement of cold-cathode tubes with solid-state electronics. This greatly reduced the detectors’ cost and size, and made it possible to monitor battery life. The previous alarm horns which required special batteries were replaced with horns that were more energy-efficient and allowed the use of widely available batteries. These detectors could also function with smaller amounts of radioactive source material, and the sensing chamber and smoke detector enclosure were redesigned to make operation more effective. The rechargeable batteries were often replaced by a pair of AA batteries along with a plastic shell encasing the detector.
In 1995, the 10-year-lithium-battery-powered smoke alarm was introduced
passes through the air being tested, and reaches the photosensor. The received light intensity will be reduced due to scattering from particulates of smoke, air-borne dust, or other substances; the circuitry detects the light intensity and generates the alarm if it is below a specified threshold, potentially due to smoke. In other types, typically chamber types, the light is not directed at the sensor, which is not illuminated in the absence of particles. If the air in the chamber contains particles (smoke or dust), the light is scattered and some of it reaches the sensor, triggering the alarm.
According to the National Fire Protection Association (NFPA), “photoelectric smoke detection is generally more responsive to fires that begin with a long period of smoldering”. Studies by Texas A&M and the NFPA cited by the City of Palo Alto, California state, “Photoelectric alarms react slower to rapidly growing fires than ionization alarms, but laboratory and field tests have shown that photoelectric smoke alarms provide adequate warning for all types of fires and have been shown to be far less likely to be deactivated by occupants.”Portable Smoke Detector
Although photoelectric alarms are highly effective at detecting smoldering fires and do provide adequate protection from flaming fires, fire safety experts and the NFPA recommend installing what are called combination alarms, which are alarms that either detect both heat and smoke or use both the ionization and photoelectric smoke sensing methods. Some combination alarms may also include a carbon monoxide detection capability.