From ancient times people have realized that early detection of fire has a positive effect in the fire control. The earliest recorded examples of fire protection can be traced back to the Roman Empire and the catastrophic fires that started in Rome. As a result, Emperor Neron has adopted regulations that required fireproof material for walls and buildings restoration to be used.
The second recorded case of adopting fire protection regulations occurred in the year 1666, after the Great fire of London, which destroyed more than 80% of the city. The fire of London spurred interest in the development of the first equipment for fire suppression in the form of hand pumps and fire hydrant installation for water supply.
Prabhat Khare, director, KK Consultants
Fire alarm systems are only effective if they can generate reliable and fast fire alerts with exact location of fire. There is a direct correlation between the amount of damage caused by fire and interventions time in various fire alarm systems. As the time of intervention decreases the damage also decreases. Hence the most important factor in a fire alarm system is the reaction or response time of fire alarm system (time between fire detection and extinguishing).
PROGRESSION OF FIRE DETECTION DEVICES
The first generation of fire detection devices (1849-1940) was based on thermal detectors. But the start of fire alarm systems development began with the invention of the telegraph by Samuel F. B. Morse in 1844. The first practical fire detection systems using telegraph, was developed in U. S. by Dr. William Channing and Moses G. Farmer in 1852.
Two years later, he applied for a patent for his electromagnetic telegraph fire protection system intended to be used in cities. In Europe in 1848 the first fire alarm device was developed by C.A. von Steingel, which was operated by the firemen and used button switches and different kinds of bells to give prearranged audio signals. The first telegraph device was created three years later in Berlin and as fire alarm telegraph equipment, used a cable connection, to alert total of 37 fire stations.
The development of the first temperature sensors started with the introduction of bimetallic sensors in the 19th century. The working principle of these sensors was based on the unequal expansion between the two metal stripes. These relays were reliable and durable, and are still considered ideal for many industrial applications.
Evolution of fire alarm systems through the years.
Fire smoke detectors are most critical and front end component of any fire detection and alarm system. These front end sensors have also evolved over the time and its’ their advancement which has contributed in making conventional, intelligent & smart fire alarm system, because without these smart, fast, reliable and addressable front line sensors, no fire alarm system could have been made smart or intelligent.
The evolution of these frontline sensors can be divided into four generations based on their developments, improvement, and merging with the electronic technology industry.
The first generation of smoke detectors started in 1930 when first electronic smoke detector was actually made by Swiss physicist named Walter Jaeger leading to the invention of the first electronic device for smoke detection. Later he developed the first patented smoke detector in the early 1940s.
The second generation of smoke detectors was developed between early 1960s until 1975, where americium 24, a radioactive source for ionization, was used for application in the electronics industry.
In 1964 an ionization smoke detector with a 24V power supply was developed by Alert. However these detectors were to be made in accordance to international rules, and also were needed to have an appropriate radioactivity label for their functioning. After detectors are used, they were to be properly disposed as a radioactive waste.
A year after the discovery of ionizing smoke detectors, Duane Pearsall has developed a photoelectric smoke detector. Major changes in smoke detectors technology occurred during the 70s and 80s in last century. These photoelectric smoke detectors operate on the light beam interruption principle, having a light source, usually white light or more often low-power laser, and a photoelectric module. A beam of light sent through the detector in normal conditions of cleanliness bypasses photocell usually at approx. 90 degrees. When smoke particles obstruct the light beam, there is a break-ray, which focused on the photo-electric cell changes the physical variables of the set limits thus triggering alarm.
The third generation of smoke detectors (1975-1990) is characterized by an increased interest in smoke detectors. In this period there were a number of key changes in the detectors design, including the replacement of the filament as a light source with a light emitting diode and the use of silicon. With the development of electronics and integrated circuits, there is a decrease in the volume of the detector components, which directly contributes to physical size reduction of the detector, a decrease in energy consumption and an improved reliability. In 1982, first analogue addressable detectors were introduced.
The fourth generation of smoke detectors (1990-present) is characterized by the use of multiple detectors in a loop, and application of algorithms. Development of microelectronics has enabled the application of many different functions. This was particularly important for all types of detectors which, through the utilization of microelectronics, can be produced as intelligent components. In this way, some basic evaluation and decision-making functions can be integrated in the detector. In 1996 a first multidetector (temperature and smoke) was developed as a detector that uses smart “OR” and “AND” logic. Major changes in smoke detectors technology were introduced by the development of smart detectors. Such smoke detectors provided option to regulate the alarm threshold via a central control panel.
During this time, along with optical smoke detector, flame detectors were also developed. Flame detectors are solutions for almost all applications, where fire may occur due to large losses of complex equipment such as oil and gas pipelines, offshore platforms, automotive manufacturing facilities, aircrafts, ships, ammunition factories, nuclear plants, and where the risk of staff injury is high. These systems use devices that match the radiation energy & are sensitive to ember, charcoal, or actual fire of sufficient intensity to activate the detector and trigger the alarm. In order to reduce false alarms due to a possible misidentification of real alarms due to any transient conditions a 2-3 seconds delay is often included in the design these flame detectors.
The first & second generation so sensors were “Analogue” however from third and fourth generations of sensors/detectors, the shift began towards solid-state sensors and later to “Addressable” type intelligent systems in which a detector compares its current sensor value with the configured threshold to make the alarm decision, which is then transmitted to the panel when the sensor is interrogated.