Video Smoke Detection Technology

Video Smoke Detection (VSD) or Video Image Detection (VID) systems have been developed to overcome many of the problems associated with smoke detection. It provides solutions for previously unsolvable fire detection scenarios, working externally as well as internally and represents a true technological breakthrough in fire detection.

VID / VSD CAMERA

 Video Image Smoke Detection (VISD) is based on the computer analysis of video images provided by integrate CCTV cameras into advanced flame and smoke detection systems. VSD automatically identifies the particular motion patterns of smoke and alerts the system operator to its presence in the shortest time possible. This enables a fast response to a potential fire, saving valuable time even in voluminous areas or where a high airflow may be present.

Smoke VID systems require a minimum amount of light for effective detection performance and most will not work in the dark, on that case used IR sensitive cameras. Flame VID systems can operate effectively in dark or lit spaces and some systems will have enhanced sensitivity to flaming fires in the dark.

In applications ranging from turbine halls to historic buildings, road tunnels, rail depots, warehouses, shopping malls, aircraft hangars and many others. Camera-based fire detection system has become established as the leading edge technology in the field of fire protection.

Fire safety professionals constantly seek the benefits of early warning of potential fires. In a perfect world it would be possible to place hundreds of smoke detecting sensors above and around any items or areas at risk. This would certainly enable a fast response to a potential fire, saving valuable time even in voluminous areas or where a high airflow may be present. But of course such a dream is not possible from a practical or financial point of view.

Video smoke detection technology makes this dream a reality.    

How it works -  Video Smoke and Flame Detection

Video smoke (VISD) and flame detection (VIFD) is performed by a software algorithm running on Visual Signal Processors (ViSPs) that implement parallel processing engines in hardware. Video images are analysed in real time by applying digital image processing techniques that allows smoke and flames to be detected with a high degree of confidence. The video image is continually monitored for changes and false alarms are eliminated by compensating for camera noise and acquiring knowledge of the camera view over time.

an illustration of how the Video Smoke Detection process works

Multiple zones can be defined for a camera view in which smoke and flames are to be detected. Each zone has a set of parameters that provide complete control over the detection algorithm. These parameters are configured individually for each zone in order to cater for a wide variety of application scenarios. It is also possible to combine information from multiple cameras to enhance the detection process.

Stemming from many years of research and development several complex statistical and geometrical measurements are made on the video image data from each zone as dictated by the control parameters. This is made possible by the parallel digital signal processing capabilities of the hardware. The scale of parameter settings is such that it is possible to detect smoke ranging from slow emerging faint smoke through to dense smoke plumes that are produced in a short period of time.

Once the measurements have been made from the video image data a set of rules can be applied to determine if they characterise smoke or flames. The rules can also be tuned to meet the specific application requirements to complete a robust and successful detection algorithm.

Video Smoke Detection Principles

VSD/VID (VISD) is based on sophisticated computer analysis of the video image seen by the CCTV camera (sensor). Using advanced image-processing technology and extensive detection algorithms (and known false alarm phenomena); the VID can automatically identify the distinctive characteristics of smoke patterns. The fire detection industry has an abundance of known smoke signatures and these are built into the system to give an accurate decision on whether smoke is present.

The VSD system uses standard CCTV equipment linked to a self contained processing system which is capable of recognising small amounts of smoke within the video image and alerting the system operator both at the processor and by a variety of remote outputs.

The VSD system employs highly complex algorithms to process video information from CCTV cameras simultaneously. The video hardware is designed to allow simultaneous real time digitising of all images, which means that the system does not multiplex images and, therefore, no information is lost or delayed. All alarm condition images are logged, time & date stamped, and stored within the system’s memory.

The VSD system detects smoke rapidly by looking for small areas of change within the image at the digitisation stage and only passing these pixel changes to the main processor for further filtering.

The video information is passed through a series of filters, which seek particular characteristics that can be associated with smoke behavior. Further analysis is then carried out on the relationships between the filtered characteristics to determine whether all the conditions have been met for the system to confidently predict the presence of smoke.

The system installer has the ability to vary the amount of smoke signal, and the length of time that the smoke exists before an alarm condition is raised to cater for situations where there may be background smoke present. The installer may also divide the video image into up to 16 zones and programmed the system to alarm only if smoke is present in multiple zones. Each zone can also be separately configured to generate an alarm at different levels of smoke activity.

The performance of a Smoke or Flame VID system must take into account three general items:

1. Fire sources

2. Environment

3. System variables

What it Overcomes

Standard smoke detection systems, be they point detection systems, infra-red beam detectors or aspirating systems all require the smoke generated from any combustion to reach them before they can recognise the particulates and activate an alarm. Such systems can function very effectively in internal thermally stable environments with low to moderate ceiling heights.

In large volumeous spaces such as enclosed sports arenas, exhibition halls, aircraft hangers and atriums, solar radiation, air conditioning systems and translucent glass all contribute to an increasing ambient temperature from floor to ceiling, known as a thermally stratified environment.

In a smouldering fire or low energy flaming fire scenario the raising combustion products cool as they rise through the air and move further away from the centre of combustion. In a temperature-stratified environment the ambient air temperature increases with height. As the combustion plume rises it cools, if this cooling reaches equilibrium with the temperature of the ambient air the smoke products will loose their buoyancy and move laterally to produce a roughly horizontal layer.  If the temperature slowly increases the hot air above the smoke will expand thus further reducing the height of the smoke stratification layer.

In environments with a high percentage change of air caused by either high velocity air-conditioning (HVAC) systems, or large open doors, smoke particles generated during low energy combustion can become quickly dispersed or diluted to the point where there are insufficient concentrations to activate an alarm in a standard smoke detection system.

These twin problems of stratification and dilution can seriously delay or even prevent a smoke detection system from entering an alarm state.

VSD systems over come both of these phenomena by looking below any stratification or dilution boundary at the incept point of any potential fire and identifying smoke generation at or very close to the source.

So, be separately configured to generate an alarm at different levels of smoke activity.

In general, VSD systems do not have fixed settings. They have many parameters that need to be adjusted to provide the optimum response to a specific fire risk. Therefore, it is very important that the manufacturer should be fully consulted in matters of product application and system design. The manufacturer’s installation, commissioning and service and maintenance instructions should also be followed.

Location and spacing

The location and spacing of detectors shall be based on the principle of operation and an engineering survey of the conditions anticipated in service. The manufacturer’s published instructions shall be consulted for recommended detector uses and locations. an engineering evaluation that includes the following:

(1) Structural features, size, and shape of the rooms and bays

(2) Occupancy and uses of the area

(3) Ceiling height

(4) Ceiling shape, surface, and obstructions

(5) Ventilation

(6) Ambient environment

(7) Burning characteristics of the combustible materials present

(8) Configuration of the contents in the area to be protected

Codes and Standards

The National Fire Alarm Code, NFPA 72-2007, recognizes the use of flame and smoke VID systems. (5.7.6 Video Image Smoke Detection; 5.8.5 Video Image Flame Detection) Per the Code, the installation of these systems requires a performance-based design. There are no prescriptive sitting requirements. Flame VID systems are classified as radiant energy sensing fire detectors and are treated similar to optical flame detectors. Due to the variability of VISD system capabilities and the differences in alarm algorithm technologies, NFPA 72 requires that the systems be inspected, tested, and maintained in accordance with the manufacturer’s published instructions.

Currently, there are no systems that are UL listed, and there is no UL standard that specifically addresses VID/VSD systems. Four systems have been FM approved. These include a system that detects only smoke, one that detects only flame and two that detect both. The systems have been approved to meet the requirements of FM Standard 3260, Radiant Energy- Sensing Fire Detectors for Automatic Fire Alarm Signaling, and UL 268, Smoke Detectors for Fire Alarm Signaling Systems.

The effect of all the changeable parameters in the VSD, such as camera lenses, software parameters adjustment and lighting conditions should be taken into consideration following the consultation principle given in BS5839 Part 1: 2002, clause 6.

BS 5839-1:2002 recognises the existence of VSD. Clause 21 j) recommends that:

"Video smoke detection systems should be capable of detecting smoke reliably in the absence of the normal lighting in the building and the absence of the mains power supply to any lighting provided specifically to aid the detection of smoke."

Environmental & Hazard Parameters

The foundational information collected for identifying typical/standard fire and smoke scenarios, likely false/nuisance scenarios, and a range of ambient conditions to which VISD systems may be subjected in the three target applications. This work included researching and reviewing fire incident data and conducting an industry workshop on VISD technology. On-site surveys and interviews with end-users were also conducted.

Installation of VSDs

Installation cables should be in accordance with the recommendations of BS 5839-1:2002.

Advantage of VISD Early fire detection

A VSD detecting fires in certain large open areas and areas of special high risk as:

1. VSD systems can be used for outdoor applications, such as train stations and off-shore oil platforms.

2. The ability of VSD to be programmed to provide different sensitivity (range) by lens selection, and to adapt to difficult application environments (false alarm sources) by tuning software operational parameters, makes it an ideal detection tool in special applications where an engineered solution is likely to give the best answer.

3. The ability to protect a large area, and/or areas with excessive ceiling heights, while still achieving fast detection. With VSD, smoke in the camera field of view can be detected whereas with other detector types, smoke has to migrate to, and be present in, the sensing area e.g. the sensing beam of a beam detector or the sensing chamber of a point smoke detector.

4. VSD, by providing accurate location of the incident, will benefit applications where targeted fire protection measures are required.

5. The ability to have live video immediately available upon detecting a pre-alarm or an alarm condition. This immediate situational awareness allows monitoring personnel to easily view the protected area to determine the extent of the fire and to more accurately identify the location.

6. Archiving of still and video images associated with alarm conditions also provides a means of assessing the cause of incidents and provides a basis for changes in the detection system if the event was a false/nuisance alarm.

7. The ability to sub-divide the image into different areas for separately identifying fire risks or programming out (masking) known sources of potential false alarms.

8. VSD, by providing visual verification of the event, will give operators information to facilitate a better and faster structured response of an incident and enable safer investigation by remote viewing.

Testing, servicing, maintenance and replacement

It is important to always follow the manufacturer’s recommendations for testing, servicing, maintenance and replacement requirements. It may be desirable that, in some installations where the effect of potential false alarm sources cannot be fully determined, a period of trial is undertaken before completing the commissioning of the system and handing it over to the client.

A method, appropriate to the risk, of testing the effectiveness of the VSD at both the commissioning stage and at subsequent service and maintenance visits should be agreed with the equipment manufacturers or system installer. Tests should be conducted and documented in accordance with this method.

VSD should NOT be used in the following situations

1. Where certain processes are likely to produce smoke-like images which may be misunderstood by the video analysis software, unless it has been demonstrated through trial and, if required, tuning of the equipment so that the effect of these false alarm sources have been adequately established and eradicated. Examples include processes generating large amounts of steam and/or other gas plumes (exhaust fumes from forklift trucks) and/or environmental pollutants (vapour, dust, sprays). In outdoor or semi-outdoor situations this may also include insect swarms.

2. Where a deterministic response to known fires is required and can be achieved by the use of EN 54 approved detectors, i.e. most standard commercial and industrial applications.

3. Where there is a danger that the ambient lighting level is either too low or too high to obtain a satisfactory response from the VSD at the time it is required to monitor the risk, unless specific provisions are available to alleviate this danger. For example infrared illumination of the scene with back-up power supply, polarized lens filters, or where very intense light sources can blind the camera.

4. Where there are significant obstructions in the camera line-of-sight of the main identified risk or where such obstructions are temporary and of an unpredictable nature.

5. Where a particular equipment configuration, including installation cables, would not assure the integrity of the alarm transmission path through the system so as to provide the desired warnings to the occupants of a building or the desired response from the emergency services.

6. Where likely environmental conditions present may have an adverse effect on the ability of the VSD to properly operate. For example this would include fog, mist, snow and rain.

7.  Where the use of cameras is not appropriate due to data protection issues.