Dousing the Flames: Fire issues move to the front burner.

Jul 25, 2007 7:20 PM  By

This is the first in a two-part series on fire safety. This week we’ll discuss what potentially causes a fire in the DC. Next week, we’ll address fire prevention.

While making physical alterations or procedural changes in DCs often leads to improvements in operating performance, those changes may actually jeopardize the facility’s fire safety measures. As Steve Musur, senior property specialist, The Chubb Corp., Chicago, reflects, “The technology changes, the commodity changes, but the building and infrastructure within the building doesn’t.” And therein lies the problem.

Consider a former manufacturing, fabrication or assembly area that has been converted to storage or warehouse space. “Even if the building contains a sprinkler system, what was adequate for the former is often no longer sufficient in its new use,” Musur explains. Similar arguments can be made when new materials are introduced into the warehouse, like aerosols, edible oils, and plastics.

Also, where a warehouse layout moves from a single row rack to a double row rack arrangement, the original sprinkler design may still offer proper protection. However, if the renovation is to multiple row racks, at greater storage heights, this is “a totally different argument now, and the existing sprinkler design may be inadequate for the new application,” he states.

“Changes made to/in the warehouse are often done solely because of space considerations and without fully understanding the ramifications to fire protection,” Musur offers.

“Changes made to/in the warehouse are often done solely because of space considerations and without fully understanding the ramifications to fire protection.” Steve Musur

“The fact that we have combustible materials vertically stacked to significant heights that can create fires that grow exponentially is something about which warehouse management should be aware,” maintains registered fire protection engineer Jeff L. Harrington, president of Harrington Group, Duluth, GA. He advises that they also should have a “basic awareness of fire behavior, fire protection systems and how they work, their importance, and most critically, a basic understanding of their specific warehouse fire hazards.”

Inside a fire

Fire prevention must be a high priority. “One of the most effective means of protecting the warehouse is not having the fire in the first place,” maintains Harrington. While sounding over-simplistic, it’s relevant, especially in a warehouse. “Once a fire gets started in a high storage array, that fire is very unpredictable,” he explains. “There’s a very rapid release of heat energy that also creates a lot of turbulence.”

A fire in rack storage of combustible commodities, he says, “has been shown by full-scale experiment to have a power-law dependence on time to the third power during the initial growth period.” This may explain why the initial attempts of building occupants to manually suppress fires in warehouses in their incipient stage so often fails, Harrington explains.

A technical report “An Insight Into Warehouse Fires” from Willis Global Property & Casualty states: “A common misconception is that a warehouse full of non-combustible products does not pose a fire hazard. However, packaging materials commonly found in use today—plastic wrapping, cardboard boxes, wooden crates, plastic or wooden pallets—all contribute to the spread of fire.” It further maintains, “Fires involving low-risk materials such as metal parts packed in cardboard will generate air temperatures in excess of 650 celcius.” Steel structures, it notes, begin to lose strength at approximately 600 celcius leading to the possible collapse of warehouse buildings within 10 minutes of a fire taking hold.

A properly designed and maintained automatic sprinkler system can keep the steel building structure cool enough to prevent failure, Harrington adds, “thus proper maintenance is critically important.”

Potential fire hazards

Many conditions can change in a warehouse that increase the fire hazard at the facility; some of these even can change on a daily basis. Common conditions which increase the fire hazard in warehouses include:

  • Use of solid shelving in storage racks; Storage placed in aisles
  • Changes in commodities stored (introduction of plastic commodities or expanded foam materials for packaging)
  • Changes in storage containers (switching from wood pallets to plastic pallets; cardboard cartons to plastic containers)
  • Changes in storage arrangement (increasing storage heights, changing the rack storage layout)
  • Bulk storage of idle wood storage pallets or plastic storage pallets; Introducing or storing flammable liquids, combustible liquids or aerosol products
  • Traffic patterns through warehouse areas involving hazardous materials used in other plant areas.

Additionally, every warehouse contains numerous potential ignition sources. The National Fire Protection Association (Quincy, Mass.) has compiled statistics on structure fires in storage properties and found that the top causes in warehouse environments consistently remain the same year after year. They include arson, hot work activities, electrical distribution equipment and fuel-powered and electrical-powered equipment.

“Chemical reactions between incompatible chemicals also have been known to ignite warehouse fires,” notes Harrington. He also advises warehouse management to focus on the leading causes of fires, some of which they can have a direct impact. Harrington focuses on three:

1. Hot work. These include open flame, sparks or other heat sources that are temporary or transient that can come into contact with combustible materials. “It’s very important that warehouse management have total control and unwavering commitment to having procedures in place,” Harrington argues. “They must also train their people and have 100% successful management of hot work activities, including having control over hot work done by outside contractors.”

Implementing a hot work permit management program is essential. The NFPA (www.nfpa.org) has a standard that can be referenced. It’s NFPA 51B, “Standard for Fire Prevention During Welding, Cutting, and Other Hot Work.” Additionally, major insurance carriers provide guidance on this subject.

2. Arson. “A lot of warehouse fires are intentionally set,” Harrington notes, “So security is very essential.” When terminating an employee or group of employees, do it in a way that minimizes the chance they can set a fire on the way out or gain entrance later to do it.

3. Lift trucks. Lift trucks were the cause of almost half of the “significant, large” warehouse fires recently studied by Harrington. Electric trucks and propane trucks are about equal in terms of their risk, he notes. He advises paying attention to battery maintenance, battery cable maintenance and the positioning of cables on operating lift trucks. Also check for loose fittings on fuel lines to avoid spillage. “It’s important not to allow heavy lift truck maintenance activities to be done inside the warehouse because it often involves hot work,” he suggests, and recommends that it be done outside the warehouse, and preferably at the dealer’s location.

This article originally appeared in the July issue of the Warehousing and Education Research Council. For more information, visit www.werc.org.

Dousing the Flames: Fire Issues Move to the Front Burner, Part II