The following are parts of two answers I submitted in one of my assignments while undertaking the Graduate Certificate course in Building Fire Safety. To understand this you may have to read the previous pages.
Q2. Discuss with reasons the fire detection and fire suppression systems that you would recommend for:
(a) A large warehouse that would be used to store over time a wide range of products. .
By Richard R. Kaiser, PE.
Article from International Fire Protection Magazine.
Fire protection for warehouses has become very complex as well because of the physical configuration of the storage, the increased values of exposed materials, and the introduction of typically more hazardous synthetics replacing natural products. A pamphlet published in 1963 by the Factory Insurance Association, in referring to the problem of adequate protection for high piled storage, stated that in a stack of burning combustibles 8 ft (2.44 m) high, 48,000 btu/min (12,096 kcal/min) were released, and from a stack of the same material piled to a height of 16 ft (4.88 m), 440,000 btu/min (110,880 kcal/min) were released. Thus by doubling the height of the pile, its burning rate was increased by a factor of 9." This statement serves as an excellent example of the challenges of high piled storage even today.
We can see from the information explained by Richard R Kaiser that warehouse storage presents a few problems as far as fire protection issue are concerned. The value of stock and the differing materials stored. Most warehouses are normally located in industrial area away from large towns and cities thus slowing down the response time from the fire service. Coupled with this is warehouses are on the whole rarely occupied throughout the night. My recommendations for the detection and suppression systems for a large warehouse would be as follows.
1. I would recommend Beam type smoke detectors these are particularly suited to large areas. This detection system would be linked to an occupant emergency warning system and to the Fire Service so that would provide a response 24hrs a day.
2. First attack Fire fighting equipment i.e. Hose reels are within 4 meters of all exits. Fire extinguishers and Hydrants would be installed at various locations throughout the site.
3. Due to the fact that warehouses have high piled storage and once a fire takes hold the smoke and heat created would present its own problems. A Zone Smoke control system would be automatically activated by the Beam type smoke detectors installed.
4. Early Suppression Fast Response (ESFR) sprinklers would also be installed as opposed to a conventional system for a number of reasons:
(a) ESFR sprinklers outputs 100 gals of water per min conventional 25-30 gals per min.
(b) The Droplet size of ESFR sprinklers are larger they are rated by the K-factor this is a constant that describes the discharge orifice providing a higher density of water at the same pressure of standard sprinklers. This prevents the water from vaporising as with the conventional systems.
(c) The sprinklers can be positioned further away from the stock alleviating the use of in rack systems.
(d) Speed. These sprinklers begin spraying water in half the time of conventional sprinklers making it more likely to extinguish rather than wetting the surrounding area.
(e) All testing and inspecting should be carried out in accordance with MS SA 76 Maintenance and testing of essential services.
(f) All employees should be trained in the use of fire fighting equipment and actions to be taken in an emergency situation.
(b) A fully enclosed high ceiling entertainment centre that can be used for basketball fixtures, concerts etc.
These types of buildings which are utilized for a whole array of activities that accommodate many members of the general public. People could also have differing types of disabilities. These factors present several problems from detection, suppression, maintenance and evacuation times.
1. Smoke detection. The average detector would find it hard to detect as smoke dilutes in high air flow spaces.
2. Heat detection. These detectors are ideally suited for confined spaces and also slow detecting fires.
3. Access for maintenance. As detectors would have to be placed maybe in an area which is inaccessible the maintenance would cause a lot of inconvenience and disruption.
4. Evacuation. This would have to be one of the main considerations as (a) We would like to avoid a premature evacuation. (b) If we did evacuate we would need the maximum time available to move people through the exits available.
Therefore I would recommend VESDA as it offers solutions to all of the above points. The system samples the air constantly, and can be placed in air ducts and areas below the ceiling level making it easy for the maintenance. As the pipe work require no maintenance and can be placed in the inaccessible areas. The most advantageous function of this system is that it can provide responses from various stages of the fire providing early warning for occupants or trigger smoke management systems and fire suppression systems. All maintenance of the installed passive and active systems will be maintained under the strict guidelines of MS SA76. Staff training will also be an added advantage to react safely in a Fire situation. Therefore the management will establish an Emergency Control Organisation in accordance with the AS 3745 2002.
(I forgot to mention the suspression systems in this one)