Shopping Center Explosion: Fluid Risk Assessment

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NIOSH recently released it’s report on the Penn-Mar Shopping Center Explosion that occured on May 7, 2008 in Prince George’s County, Maryland. Report Copy HERE. A number of mission critial lessons and insights can be gained regarding initial response, command management, operational safety, tactical deployment and effective situational awareness and dynamic risk assessment through an unstable progressing incident. Here are some of the insights and specifics.

At 12:54 PM on Thursday, May 7, 2009, Prince George’s County Firefighter/Medics were dispatched to respond to the Penn-Mar Shopping Center, a large 1-story strip mall, in the 3400 Block of Donnell Drive in Forestville and arrived at 12:59 PM.  First arriving crews initiated an investigation into a strong odor of natural gas inside the businesses.  Firefighters evacuated 5 of the 6 stores that were in the area of the odor, a sixth store was vacant. 

  • Forty-five people were evacuated from the 5 stores and firefighters then started ventilation efforts and called for assistance of the Washington Gas Company.  Firefighters discovered natural gas bubbling up from the ground on the exterior rear of the vacant store and minutes later reported that there was a fire on the interior. 
  • Within a minute, at about 1:20 PM, a massive explosion occurred. 
  • A MAYDAY call was sounded and additional resources including paramedics and a second alarm of firefighters were summoned to the scene.

Large plate glass windows blew shattered glass and other debris 60-70 feet into the front parking lot, the roof assembly appeared to have been lifted up and then fell back into place and the rear brick and block wall was completely blown out.  Firefighters were in the direct line of the explosion and suffered burns and injuries from flying debris.  Firefighters were wearing their personal protective gear which is believed to have minimized injuries.  They quickly gathered themselves and checked on other crew members and civilians that may have been injured.  A total of eight firefighters sustained a variety of injuries ranging from lacerations to second degree burns.  Four Firefighters were transported to the Washington Hospital Center Burn Unit where two were treated and released and two were admitted for additional treatment.  While initially transported with serious injuries, the firefighter’s conditions have been upgraded to “good.”  Four other firefighters were transported to other area hospitals and were treated and released.  One civilian, an employee of the Washington Gas Company was also treated and released from an area hospital.  There were no injuries to any of the 45 evacuated civilians. 

 3-18-2010 9-29-48 PM

A small fire resulted from the explosion that was quickly contained and extinguished.  The investigation so far has determined that the release of natural gas occurred in the vacant store and reached an ignition point that resulted in the explosion.  The Fire/EMS Department’s Technical Rescue Team completed a through secondary post-blast search of the damaged stores confirming that everyone heeded the orders of first arriving firefighters to evacuate.  (Excerpt from PGFD Press Release 05.07.2009)

 3-18-2010 9-09-52 PM

Building Knowledge

The south side of the structure was comprised of 10 business spaces (three of which were vacant) in a strip mall designed and constructed as a Type II, noncombustible classification in the 1970s. The section of the commercial structure involved in the incident was comprised of a main 2 story building, which included 2 vacant businesses and a mall office, with an adjoining wing on the right consisting of 6 businesses (1 unoccupied) in a single story with high dropped ceilings, large attic void spaces, and a sprinkler system. In the wing along the C-side were utility rooms housing the electrical circuit panels, sprinkler system controls, and security panels. It was constructed of brick/block and mortar with large plate glass windows on the A-side, block and mortar exterior C and D-side walls, and a block and mortar interior B-side wall adjoining the rest of the structure. The roof was a commercial flat roof consisting of open web, steel bar flat roof trusses covered with corrugated metal “q-deck” with multi-layered plies of bitumen laminated roof felts and topped with a granule-surfaced cap sheet. The open web steel bar roof trusses were connected to a steel beam and column structural assembly system.

The interior walls separating the businesses were primarily light weight galvanized metal studs covered with a ½ inch gypsum wall board providing tenant separation and compartmentation. The ceiling was a suspended acoustic tile ceiling system which provided a common void space over the business occupied areas of the adjoining right wing. The businesses contained office furniture, partitions, restaurant equipment and supplies, and health and beauty equipment and products.

NIOSH Report Summary

On May 7, 2009, two captains, a lieutenant, and five fire fighters were injured during a natural gas explosion at a strip mall in Maryland. At 1254 hours, dispatch reported a natural gas leak inside a business at a strip mall. Five minutes later, the initial responding crew and the incident commander (IC) arrived on scene to find a gas company employee looking for an underground gas leak. Approximately 6 minutes later, a natural gas leak was found near the exterior rear corner of the structure. After 23 minutes on scene, approximately 45 civilians were evacuated from 7 occupied businesses.

A captain exited the rear door of the business that had called in the natural gas leak and noticed fire along the roof line. Crews in the front and rear of the structure had begun to pull hoselines as another captain was looking out the rear doorway of a middle unoccupied business and noticed the electric meter located on the exterior wall on fire. Anticipating an explosion, he tried to leap out the rear doorway. At the same time, a fire fighter had entered the front door of the unoccupied business, noticed the heavy smell of natural gas, and felt air rush by as the structure exploded. Debris and fire blew out the front, rear, and roof of the structure. The captain who tried to leap out the rear doorway was blown into the rear parking lot and the fire fighter who had entered the front of the structure was blown out the front door and covered with debris. Numerous other fire fighters, primarily near the front of the structure were blown off their feet and hit with debris.

An uninjured captain issued a Mayday, followed by the IC ordering evacuation tones and a personnel accountability report. Crews began to look for the captain who was blown out the rear doorway. He had walked around the side to the front of the structure, and radioed his location to command. Fire fighters began moving injured personnel to ambulances staged in the front parking lot. Eight fire fighters and a gas company employee were transported to local hospitals. The injuries ranged from third degree burns to an ankle sprain.

Key contributing factors identified in this investigation included: insufficient execution of the fire department’s updated standard operating guidelines (SOGs) on incidents involving flammable gas, e.g., apparatus and fire fighters operating in a flammable area (hot zone); the accumulation of natural gas in the structure’s void spaces; unmitigated ignition source; insufficient combustible gas monitoring equipment usage and training; and, ineffective ventilation techniques.

NIOSH investigators concluded that, to minimize the risk of similar occurrences, fire departments should

  • ensure that standard operating guidelines for natural gas leaks are understood and followed
  • contact utility companies (natural gas and electric) immediately to cut external supply/power to structures when gas leaks are suspected
  • ensure gas monitoring equipment is adequately maintained and fire fighters are routinely trained on proper use
  • ensure ventilation techniques are conducted after ignition sources are mitigated
  • ensure that rapid intervention teams are staged at the onset of an incident
  • ensure that collapse/explosion control zones are established when dealing with a potential explosion hazard

Although there is no evidence that the following recommendations would have prevented these injuries, they are being provided as a reminder of good safety practices.

  • provide manual personal alert safety system (PASS) or tracking devices to locate potentially missing fire fighters when SCBA are not utilized
  • ensure standard operating guidelines for communications are understood by dispatch
  • ensure adequate staffing for emergency medical services and rapid intervention teams (RITs)
  • ensure training is evaluated for rank and skill levels across the combination department personnel

Contributing Incident Factors

Occupational injuries and fatalities are often the result of one or more contributing factors or key events in a larger sequence of events that ultimately result in the injury or fatality. NIOSH investigators identified the following items as key contributing factors in this incident that ultimately led to the injuries of eight fire fighters:

  • Insufficient execution of the fire department’s updated standard operating guideline on incidents involving flammable gas, e.g., apparatus and fire fighters operating in a flammable area (hot zone).
  • The accumulation of natural gas in the structure’s void spaces.
  • An unmitigated ignition source.
  • Insufficient combustible gas monitoring equipment usage and training
  • Ineffective ventilation techniques.

Building Knowledge=Fire Fighter Safety

When was the last time you and your company took a good look around some of your commercial shopping centers, strip centers, malls and business retail complexes? There is a wealth of mission critical information to be gained by conducting a basis walk through and looking at some key construction, configuration, layout and access and utilities features.

Take note of the structural systems that comprise the roof assemblies and the wall and supporting interface. Identify the basic volume of the commercial spaces paying close attention to the common tenant storage, storerooms, access and transfer loading dock and delivery areas.  Focus and take note of the fire loading and its expected degree of fire behavior and intensity. Check out the condition and operability of the fixed suppression systems and the integrity of fire barriers and separations.

There’s so much “free” data and information to be gained by going “shopping”; all of which will transcend and can be retrieved at such time a response materializes at that location in the future. If you can, capture the pertinent information into your pre-fire planning data base and make sure you discuss and share your observations, postulated strategies and tactics around the kitchen table or as a table top exercise or better yet in the form of an on-site drill or multi-company training exercise.

Be prepared for the unexpected and always use extreme caution and heightened situational awareness and fluid risk assessment and reconnaissance processing to stay atop of any undefined and evolving incident. Do not allow the potential lack of severity; of what may have all the indications of an unremarkable/uneventful and common call run such as a gas odor investigation or a natural gas leak cause your companies to have less than a high level of alert, focus and attentive accretions through all phases and deployments of the incident. Don’t become complacent.

In addition, take a look at some information relate to another tragic incident response to a reported gas leak that occurred in December, 1983 that lead to five fire fighter LODD’s in Buffalo, New York. HERE

Archived Report From STATter911, from May, 2009 HERE and recent 2010 update HERE with fireground Audio

Prince George’s County (MD) Fire Press Release from May 7, 2009, HERE

Slide Show from HERE 

BING mapping Images, HERE

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