07 Oct Maximum foreseeable loss
Maximum Foreseeable Loss (MFL) events are caused by one of three main events. These events are fire, explosion or equipment failure with fire being the primary cause. B. Aaron Johnson, Fire & Building Code Strategist, and Justin Biller, p.e., fsfpe consider the contribution of fire doors to MFL scenarios.
Wednesday, August 12th, 1953 started like any other for the 3,200 factory employees at the General Motor’s plant in Livonia, Michigan. Workers manned their machines, on the assembly line, building transmissions for Cadillacs, Oldsmobiles, and Pontiacs. No doubt, they were looking at their watches as the four o’clock shift change approached. However, this day would not end as all the others had. This day would end in disaster.
By the end of the day, five would be dead and scores injured in a fire that completely destroyed the plant. The damage was an estimated $35 million (approximately $337 million in 2019 dollars) to the structure, contents, and equipment. And multiple millions more in lost time, and lost work. The ripple effect of this incident resulted in nearly 45,000 employees across the country being temporarily out of work.
A combined investigation by FBI, insurance, and law enforcement agencies determined that the fire was
caused by a spark from a welding torch. As the welding operation was taking place on a steam pipe above the plant floor, sparks dropped into an oil dip tank trough. More than thirty apparatus, and 150 firemen, from nine different fire departments, responded to the blaze. They could only save an office building and small power plant. Nothing else of the four year old plant could be saved.
How did this 1.5 million square foot factory, said to be equipped with the “most modern fire prevention and fire quenching equipment”, become one of the nation’s largest insured fire losses? An article in the September 1953 edition of Fire Engineer stated, “To the workers, and the official GM family, the building and production processes measured up fully to all established fire and safety codes.” However, the fire marshall’s report would show that the building was only partially sprinklered (perhaps only 10-15%), and had been added on to several times, with no fire stops built into place. This incident demonstrates what is referred to today as a or Maximum Foreseeable Loss (MFL).
An MFL is a scenario that accounts for an event in which the largest loss to an organisation may occur. This allows planning and mitigating factors to be identified and put into place to avoid such an incident. This loss can be in the form of physical loss to the structure or a business loss. The term is used by insurers and defined by FM Global. MFL scenarios are often developed for the largest and most complex facilities. These may include large warehouses, manufacturing and processing plants, or chemical and storage buildings. Generally, these types of buildings will be required by code, and the insurer, to have automatic fire protection components in place. These systems, naturally would be designed to prevent a large loss. The MFL scenario assumes that these systems are impaired. If these systems are impaired, how can loss be minimised?
Maximum foreseeable loss events are caused by one of three main events. These events are fire, explosion, or equipment failure. Fire is the primary cause of an MFL. Uninhibited, fire will spread and be permitted to spread until all fuel is consumed. Think of a large warehouse, or warehouse membership type store. These types of places are filled with wooden pallets, plastic, paper, packaging, and the products themselves. If a fire were to occur, and there was no automatic fire protection in place, the abundance of combustibles and their storage arrangement, would fuel a fire for a very long time, and lead to massive loss.
Within certain types of facilities, explosion risk is an inherent part of the regular activities. Fuel processing and storage facilities, fertiliser plants, manufacturing facilities, all engage in operations that can come with a high risk of explosions.
Equipment failure can also lead to catastrophic loss. The failure of machinery can lead to one of the other types of MFL events, such as a fire or explosion. Additionally, equipment failure, especially highly specialised equipment can lead to devastating financial loss.
The MFL scenario asks, and answers, the question “If the automatic fire protection systems, designed to prevent large loss, are impaired, what other steps can be taken to prevent this loss?” After every major incident, the after-action reviews always include the question, “What could have been done to avoid or limit the extent of damage?
Equipment failure can be mitigated through proper monitoring, preventative maintenance, and timely capital replacement plans. Explosion risk can be reduced through improved process safety and supervision, and separation of materials. Fire spread in large buildings, however, may only be mitigated through the construction features of the building itself. These features should include an MFL fire wall. FM Global Data Sheet 1-42, Maximum Foreseeable Loss Limiting Factors, and NFPA 221, Standard for High Challenge Fire Walls, Fire Walls, and Fire Barrier Walls outline the construction requirements for the MFL fire wall, or high challenge fire wall.
The objective of the MFL and high challenge fire wall is to stop the spread of fire and contain it to only the side of origin. These walls are to be constructed as non-load bearing only, and must be constructed to a 4-hour fire-resistance rating. The design of the wall is to be such, that it would remain standing and stable in the event of a structural collapse. The wall should be designed to prevent the spread of fire “through, under, over, or around”. This means the wall must be built all the way out to, or through, the edges of exterior walls and roof line. Every effort should be made to prevent penetration of the wall. However, if it is necessary to penetrate, penetrations cannot be higher than 36 inches above the finished floor, and must be protected with an approved 4-hour rated fire stop system. Fire protection doors and frames are permitted to be installed in the wall, but they must be a minimum of 3-hour fire protection rating and cannot have any glazing in the door.
Since the intrinsic protection of MFL and high challenge fire walls is reliant on proper fire protection of openings, fire protective doors and frames are a major concern for building owners and facility managers when considering fire resistive construction within their buildings. A standard door test with specific hourly ratings, as the industry is now familiar, was first established in the early 1940s by the American Society of Testing and Materials (ASTM) and the National Fire Protection Association (NFPA). The basic testing procedures covered in those standards have essentially remained constant to the original testing concepts.
Ongoing maintenance of doors and architectural hardware represents a significant cost margin to building owners. Maintaining all doors in large facilities is always a challenge, but of even higher concern for facility engineers is fire wall and barrier management, wherein door maintenance is a highly critical component. The added strain on fiscal responsibilities for facilities to “do more with less” heightens the need to challenge installers to do the work right the first time – it is often noted on annual inspections of fire and smoke door assemblies that the ongoing challenges to maintenance stem from improper installation (i.e., improperly plumbed door frame and jamb, incorrect or insufficient hardware, incorrect door or glazing type, etc.).
According to the Door Security and Safety Foundation, although doors only represent approximately two percent of a typical construction budget, more than 30 percent of punch-list items are on average door-related. It is therefore the opinion of many within the industry that building owners should require verification that fire doors and other protective openings are installed properly from the outset – a determination that committee members of NFPA 80, Standard for Fire Doors and Other Opening Protectives also found imperative. In its most current published editions (i.e., 2016 and 2019 editions), NFPA 80 prescribes in section 5.2.1 that “upon completion of the installation” these assemblies are to be inspected and tested. It seems that a comprehensive survey of door installation during construction benefits the building designer and can dramatically decrease ongoing maintenance costs associated with fire and smoke door assemblies. This can be done as an integral part of fire system commissioning or it could be done stand-alone with the building design team.
The National Fire Protection Association (NFPA) in its report, Fire Loss in the United States During 2017, claimed that fires cost a $23 billion in loss for the year. In nearly 1.5 million fires for the year, 22 could be considered large-loss. However, these 22 fires accounted for 54.5 percent of the total dollar loss. These 22 fires, also resulted in 52 deaths and more than 200 injuries.
With the high toxicity and combustibility rate of the products humans consume today, passive fire protection features in these large warehouses and manufacturing facilities are more important than ever. Today’s passive fire protection features like MFL fire walls, fire rated doors, and their proper maintenance will prohibit large loss incidents.