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Smoke Detectors

Smoke detectors are devices designed for the early detection of smoke, most often originating from an incipient fire. They are used as standalone fire alarms or interconnected. Depending on the functions of the detector, it may have audio and/or visual signals to warn of fire danger. Other detectors transmit the detected data to connected control panels, which process and evaluate it. Detectors have been protecting commercial and residential buildings, other properties, assets, and most importantly, people themselves for several decades. By providing early warning of potential danger, they offer the opportunity to extinguish a fire in its early stages or to evacuate the premises. Many people owe their lives to smoke detectors. When connected to firefighting systems, they can quickly summon professional help.

Households particularly appreciate the options of autonomous detectors with integrated signaling functions, also known as fire alarms. Commercial buildings, hospitals, offices, and other public facilities install central fire systems, allowing them to monitor the status of the entire building and data from dozens of detectors simultaneously from one room.

The most common dimensions of detectors are around d= 150 mm and a height of 25 mm. The shape of detectors resembles a disc, but it depends on the innovation of individual manufacturers.

Types of Detectors

Detectors operate based on two principles - physical and optical. From a physical perspective, we distinguish ionization detectors, and from an optical perspective, photoelectric or more commonly called optical detectors. 

Ionization detectors detect smoke using two chambers. One chamber is sealed and serves as a reference. The other chamber is open to the surrounding air. Ionization of the air occurs in both, followed by the evaluation of the measured electric current flow. The results are constantly compared between the two chambers to check for deviations in the open chamber. If smoke particles enter the open chamber, some ions attach to them and stop conducting electricity. The detector records the resulting difference in electrical flow and triggers an alarm. Ionization in both chambers occurs due to the radioactive element Americium-241, but it is such a small amount that it only causes a very low level of radiation outside the device. Ionization detectors thus do not pose a significant radiological risk and are safe for the surroundings unless there is forced entry into the ionization chamber of the alarm. The chamber itself acts as an ionization shield for radiation. The risk of exposure from an ionization detector operating in the usual way is much lower than natural background radiation.

Optical detectors feature a light source that passes through the air and records any deviations in light intensity caused by smoke, dust, or other airborne substances. This can involve infrared, visible, or ultraviolet light, with the source being either a bulb or an LED, as well as a photodiode (lens with a photoelectric receiver). For smaller spaces, a point detector suffices, illuminating the air flowing in its chamber and thus detecting smoke from a nearby fire based on suddenly scattered light. Alternatively, smoke entering the chamber scatters the light beam, triggering the alarm. For larger spaces, such as atriums and auditoriums, detectors with optical or projected beams are more suitable. The detector emits a beam of infrared or ultraviolet light, which is received either by itself or by a receiving reflector. If the received light beam is weaker due to smoke, the detector triggers an alarm.

Optical detectors are often found in a combined variant with a heat sensor. Such a variant ensures a higher improbability of false alarms. 

Optical and Ionization Detectors Regin

  • for ducts, pipes, and ventilation
  • to the control panel or standalone
  • LED indication
  • service alarm
  • flow indicator

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Which Type to Choose?

Each type has its pros and cons and it depends on the space where the detector is to be placed. Ionization detectors are more sensitive to small smoke particles from fast-burning fires, while photoelectric detectors, on the other hand, detect smoke from smoldering fires more quickly, which is particularly useful in households where there is a risk of electrical fires or kitchen fires during baking and cooking. Ionization detectors placed near kitchens and garages more often trigger false alarms, to which they are generally more prone. With optical detectors, care must be taken with dust and insects, as there is a risk of blocking the light beam.

According to studies conducted by various countries, optical detectors respond to incipient fires manifesting as gradual smoldering more quickly than ionization detectors. This is a difference of tens of minutes, allowing for timely evacuation and summoning of firefighting assistance.

In the case of fires with a rapid onset and invisible smoke particles, ionization smoke detectors are a better option. They are also more suitable for detecting dark to black smoke, while optical detectors better recognize white to gray smoke. Therefore, an ideal choice would be a combination of both types of detectors or a combination of an optical detector with a heat sensor.

New Developments in the Smoke Detector Market

Recently, there has been an increase in the number of aspirating smoke detectors (ASD) on the market, which can be used in complex fire protection systems of large buildings. This is an advanced and highly sensitive technology that draws air from each room through small tubes. The air is then analyzed and evaluated based on the data collected from all rooms. If smoke particles are detected in any room, an alarm is triggered. Aspirating detectors are particularly suitable in areas with increased air flow, where optical and ionization detectors might not detect smoke in the early stages. They are also suitable for rooms with a higher potential risk of ignition, such as computer rooms.

Autonomous Detectors and Alarm Systems

Detectors can serve as standalone fire alarms or be interconnected in a fire protection system. 

In households, standalone detectors, which also serve as fire alarms and emit a loud sound signal, are most commonly used. Some can be interconnected so that a detector that detects a threat in one room also triggers alarms in other rooms. However, the sound signal is often the only response these detectors are capable of in the event of a threat. The connection can be either wired or wireless.

Some detectors only serve as sensors and send collected data to a connected control panel, which analyzes and evaluates it, and in the event of deviations from the norm, triggers the appropriate warning devices. 

Smoke Detector Regin

  • for all spaces
  • to the control panel
  • powered through the control panel
  • wired connection

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What to Consider When Choosing a Detector for Your Home?

It is advisable to consider how many rooms we have in the household and how far they are from each other. Also, whether we need detectors that warn of danger only locally or also remotely through remote communication. Autonomous detectors functioning only as a siren and visual alarm are the cheapest option. They warn of danger only in the room where they are installed, which can be sufficient in a small apartment, as the sound alarm can be heard in the adjacent room. However, if we are away from home, we will not receive any notifications about an incipient fire and cannot prevent damage. 

For a family house, it is definitely worth having more interconnected detectors to ensure the audibility of the alarm on all floors and rooms. In such a case, it is not a bad idea to equip interconnected alarms with remote communication, which will send fire information to a mobile device and help prevent greater property damage.

Smoke Detector Honeywell

  • battery-powered
  • wireless communication option
  • optical principle
  • light and sound signaling
  • ceiling and wall mounting
  • protects the whole family

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What Detectors for Commercial and Other Buildings?

For large, but also small, commercial buildings, it is certainly more practical to install a comprehensive fire alarm system consisting of detectors, control panels or control centers and alarm and warning signaling. Detectors for these systems tend to be more expensive than autonomous battery-powered detectors. They find application in commercial and industrial buildings, hospitals, but also on ships, trains, and in some households. The detectors themselves do not have sound and visual signaling but send data to the control panel, which, after evaluation, triggers external warning devices. The control panel can secure various levels of threat and, in addition to external warnings, can control more complex functions, such as evacuating people and so on.

How Can Detectors Be Connected to the Control Panel?

An older but still used method of connection is parallel connection, where the control panel processes the signal from several detectors connected in series. Such connected detectors form one zone, and multiple such zones can be connected to the control panel. The control panel perceives each zone as a whole. It can determine which zone indicates an incipient threat but cannot specify which particular detector recorded it. If we do not need to know the exact location of the threat, this system will suffice.

Today's systems, however, offer the possibility of clearly identifying which detector recorded the threat. The control panel still monitors individual zones, but in each zone, it can precisely identify the detector indicating danger. Each detector in the system receives its own number or address to be immediately identifiable on the control panel. These systems are generally more expensive to acquire but also offer additional functions that older, classic systems lack. These functions include, for example, different sensitivity modes depending on the time of day, identifying system errors, graphical display of detectors on the control panel, and more.

Smoke Detection Control Panel Regin

  • for detectors S65... and SDD...
  • connection of up to 20 detectors
  • two external alarm outputs
  • 3 LED diodes
  • wired connection

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Where to Best Place the Detector?

The most common placement of detectors is on the ceiling or wall, where they can best detect rising smoke, which naturally rises upwards. It is also advisable to place the detector directly in a room with a potentially threatening risk (kitchens, workshops, boiler rooms, etc.). However, placement in connecting rooms, such as staircases or hallways, will yield the same result, albeit theoretically delayed by a few moments. At the same time, the likelihood of a false alarm is reduced. A recommended room for installing a smoke detector is the bedroom, as a person in sleep loses the ability to smell smoke and react in time. The detector is mostly fixed in place using screws.

Types of Warning and Alarm Signaling

The classic method of signaling is sound and visual warning in the form of a loud tone and flashing light. Some detectors have the option of muting or temporarily silencing using a button on the cover, which is especially useful in cases of false alarms in places where they may occur quite often (e.g., near the kitchen). However, there are also alarm devices with tactile alerts, vibrating pads, flashes, or remote warning headphones, which are intended primarily for at-risk groups of older people and the deaf, who might not wake up to a regular alarm. For these groups, lower-frequency sounds also work better.

Powering Detectors

Detectors can be powered from a central alarm system or removable rechargeable batteries. Central alarm systems of large commercial or industrial buildings are powered from the network with a backup battery so that the system does not fail even in the event of a power outage. Cheaper autonomous detectors are often powered by rechargeable or disposable batteries, which need to be replaced over time. Some detectors have a battery only as a backup power source in case of a power outage. In the case of a weak or depleted battery, detectors chirp to alert for replacement. It is recommended to replace the battery at least once a year.

Should I Get a Smoke Detector for My Home?

Definitely yes. While commercial and other buildings have the presence of a central alarm system mandated by the government, in apartments and family houses, especially older ones, it often depends solely on the owner's will. It is stated that the risk of death in a fire is halved with the presence of a functional smoke detector. Firefighters strongly recommend installing a detector. Even a cheap autonomous smoke detector can save lives and protect property from damage.

How Soon Should a Smoke Detector Be Replaced?

A smoke detector lasts approximately 8-10 years. After that, it is better to replace it with a new one. Regular checks and replacing the batteries at least once a year are recommended.

What Does Czech Legislation Say?

The necessity of having a smoke detector in a building, apartment, or house is enshrined in Czech legislation since 2008. Any new construction or renovation requires the acquisition and installation of autonomous detection and signaling. In the case of apartments, each unit must be equipped with one smoke detector, which is placed in the part of the apartment through which the escape route leads. If the apartment is larger than 150 m2, or if it is a duplex apartment, it must be equipped with an additional appropriately placed detector.

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