Non-addressable, addressable, addressable-analog fire smoke detectors. Advantages and disadvantages.
Hardly anyone doubts that fire protection (in terms of fire alarms) of most premises with a standard ceiling height and the absence of any special technological processes or stored substances (for example, flammable liquids) must and is sufficient today to carry out smoke point fire detectors.
The category of smoke detectors includes both optical-electronic and ionization fire detectors. Ionization (radioisotope) detectors have a simpler design and, as a result, lower cost and price. However, if we take into account the need to dispose of these products at the end of their service life with the corresponding costs for this procedure, the positive price factor ceases to be indisputable. Research of the world market of smoke fire detectors by sales in 1984 gave a result in favor of radioisotope detectors in a percentage ratio of 80/20, and similar results in 2004 showed an inverse situation in favor of optical-electronic detectors in a ratio of 90/10.
Both domestic and foreign manufacturers of technical means of fire alarms define today a wide range of smoke optoelectronic fire detectors with various technical parameters and functional capabilities. In accordance with the terminology adopted in GOST R 53325-2009 on the principle of transmitting information about a fire hazardous situation from protected premises (smoke — optical density of the environment), detectors are divided into non-addressable, addressable and addressable-analog (analog). Algorithmic methods of electronic processing of useful information in the detectors under consideration are of different nature. This can be a simple excess of a predetermined threshold of an electrical signal depending on the concentration of smoke (local in time), to multi-channel processor processing of this signal with automatic adaptation and correlation of the final result with previous information for the previous period of time, which can have a different value, calculated in hundreds of hours.Historically, threshold (non-addressable) smoke fire detectors were the first to appear, which, when the radiation source in the smoke chamber was replaced with an incandescent lamp by a LED, became widespread. Non-addressable detectors are used in radial structure fire alarm systems by connecting them in parallel to two-wire loops of non-addressable fire alarm control panels (FACP). The number of detectors in a loop can be limited only by their total consumption current, and the alarm signal «fire» sent to the FACP is the same when any detector in the loop is triggered, which does not allow identifying it and determining the room in which the fire occurred.
The approach to the formation of technical requirements in regulatory documents for non-addressable fire detectors causes some confusion. Instead of initiating the improvement of non-addressable fire detectors that occupy their niche (in terms of technical and economic parameters), clause 4.2.5.1 of GOST R 53325-2009, for example, even allows the absence of optical indication in the connected state for the detector type in question.
The appearance of addressable smoke fire alarms dates back to the 70s of the last century. This is closely related to the development of electronics, and above all, with the appearance of general-purpose industrial microprocessors, which were first used in addressable fire alarm control panels, and then in addressable fire alarms. The essence of addressable systems and addressable fire alarms is to link the transmitted signal of the «fire» alarm to the conventional number of the fire alarm that registers the fire. Thus, identification is carried out not with an accuracy of up to the definition of the loop (as in non-addressable systems), but with an accuracy of up to the fire alarm. In advanced addressable systems, the digital information communication channel in the form of an addressable alarm loop is used for two-way (interactive) transmission of addressable information in order to control various functional modules of the periphery and to expand the functionality of the addressable fire alarms themselves.
Addressable analog fire alarm systems were a logical continuation of the development of digital information processing in addressable systems. However, there is a fundamental difference between analog fire detectors and all others that preceded them. This primarily concerns the prerogative of switching on the alarm signal «fire», which in analog systems passed from the fire detector to the fire alarm control panel, and the detectors turned into sensors of analog information, which contains a quantitative characteristic of the corresponding fire factor (for example, a thermal fire detector has become, in fact, a remote thermometer).
The main advantage of addressable analog fire alarm systems is the huge hardware and software resource of the fire alarm control panel compared to a fire detector, which allows for prompt monitoring and control of the system in real time across the entire periphery (fire detectors and functional modules), taking into account previous states. An example is the ability to programmatically change the sensitivity of fire detectors (day-night mode), as well as the correlation of the response threshold of a specific detector depending on the information received from other detectors located nearby.
Regulatory documents defining the list of requirements and application of technical means of fire alarm (including smoke point optoelectronic fire detectors) can be divided into three territorial groups. In the Russian Federation, these are Fire Safety Standards (FSS) and GOST R 53325-2009 (together with SP), which are conditioned by the relevant federal laws, although they have some fundamental differences in terms of technical requirements. In Europe, this is a set of regulatory documents EN 54, and in North America — UL 217 and UL 268.
The sensitivity of smoke detectors in accordance with GOST R 53325-2009 should be within the range from 0.05 to 0.2 dB/m. In America, this value is significantly wider (~ 0.05 — 0.5 dB/m), and in Europe, the upper limit does not exist at all (the lower limit of the numerical value is 0.05 dB/m). Obviously, one of the main advantages of addressable analog systems — the ability to change (within the permitted limits) the response threshold of smoke detectors in the Russian Federation is becoming ineffective, and often completely disappears due to the small dynamic range of permissible sensitivity change. In addressable analog fire alarm systems, the consequence of the possibility of a higher data transfer rate (in comparison with similar addressable ones) is higher requirements for cable products (twisted pair, shielded wire, etc.), as well as the use of additional measures to ensure the appropriate level of electromagnetic compatibility.
High-quality developed and manufactured smoke point optical-electronic fire detectors in compliance with the required technological processes and with the necessary types of testing are the key to success in improving fire safety in general.