Details Matter: It’s in the Attic!

By Sean Gray and P.J. Norwood
Norwood1
(UL FSRI photos)

Attic fires can be some of the most challenging fires to extinguish. These fires can be extremely dangerous because the true conditions are hidden in the attic space and firefighters may not be expecting the sudden change in conditions when an attic flashover occurs. Many times, during size-up, the smoke conditions and location will confirm an attic fire. The next questions that should come to mind are the following:

1.      How did the fire get into the attic?

2.      Can it safely be extinguished?

3.      Where should the initial hoseline be placed?

It also needs to be understood that when opening the ceiling to access the attic, you’re creating a ventilation opening. It must be done, but firefighters should put water into the attic space to cool it off immediately. Significant firefighter safety research was done on attic fires. This article shares the highlights.

UL-FSRI Research Study Purpose

The purpose of the study was to increase firefighter safety by providing the fire service with scientific knowledge on the dynamics of attic and exterior fires and the influence of coordinated fire mitigation tactics from full-scale fire testing in realistic residential structures. Attic fires impact every town and city across the United States. It is estimated that 10,000 residential building attic fires are reported to U.S. fire departments each year. These fires cause an estimated 30 civilian deaths, 125 civilian injuries, and $477 million in property loss. Some factors that contribute to these statistics follow.

  • Attic fires commonly go unnoticed until smoke or flames are visible from the outside of the structure.
  • A fire in the attic may involve insulation and wood structural members as well as a variety of stored belongings.
  • Attic ventilation systems create an optimal fire growth and spread situation by supplying oxygen to the fire and exhausting hot gases. 

Experiments included wall experiments, eave experiments, full-scale attic fires, and knee wall and attic fire experiments. At the end of the experiments, all the data was analyzed, and the Technical Panel was compromised of fire service personnel from across the country. This analysis allowed the panel to design a list of tactical considerations. These considerations are not rules that must be followed. They are not tactics that UL indicates you only use at your next attic fire. They are considerations for use in your standard operating guidelines, in training, and on the fireground. The panel defined 12 tactical considerations, which follow.

Tactical Consideration # 1

Increased use of plastics in exterior walls will change what you find on arrival. Changes in residential wall construction methods are playing an important role in how exterior fires are initiated as well as how they spread and extend.

Exterior wall fires spread more rapidly. The evolution in building materials has led to an increased ignition potential from fires. These new materials also have much higher energy release rates. This combines to change the way fires grow and spread on the exterior of a structure.

Exterior fires can easily become structure fires prior to arrival. Fires adjacent to modern exterior wall construction have the potential to transition to structure fires within two minutes of ignition.

Exposure to adjacent structures occurs prior to arrival. The projection of the flames out of the eaves and the additional fuel load at the eave/soffit line combine to increase the radiant energy directed at any adjacent structures, increasing the exposure threat.

Tactical Consideration # 2

If the fire starts on the outside, start fighting it from the outside. Rapid water application to knock down the exterior fire is a critical part of any attempt to control not only the fire’s spread to adjacent structures but also the fire’s migration into the interior of an exposed building. If the source of the fire is not suppressed, it will continue to supply heat energy to the fire developing on the interior, worsening conditions on the inside and in many cases making it impossible for the interior crews to maintain or advance their positions

LODD Case Studies:

  • Prince William County Department of Fire and Rescue, LODD Report for Technician I Kyle Robert Wilson–NIOSH LODD 2007-12
  • Four Career Fire Fighters Injured While Providing Interior Exposure Protection at a Row House Fire–District of Columbia–NIOSH LODD Report 2007-35

Tactical Consideration # 3 

Learn to anticipate where and how an exterior fire will migrate to the interior. Exterior wall fires may easily spread to the interior at locations other than the eaves and soffits.  Any penetrations such as air vents, electrical receptacles, plumbing penetrations to faucets and drains, and especially windows provide the opportunity for fire spread into the interior of the structure. Leaving the interior fire barrier in place until the exterior fire can be controlled will limit the extension into the structure.

Tactical Consideration # 4

Attic fires are commonly ventilation-limited fires. The openings provided for natural ventilation are not enough to maintain steady state burning and fuel-limited fire behavior. The size of the fire is limited by the available oxygen and will nearly always become ventilation-limited.

Accessing the attic: Controlled openings created between the neutral plane (such as through the ceiling below the attic space) will not cause immediate growth and can provide access for suppression.

Small vs. large hole: A small opening in the ceiling will supply some air to the attic fire, but without an outlet like open gables or a large hole in the roof, there is not a flow path through the attic enough to lead to rapid fire growth. There will be local mixing of fuel and air at the opening that will produce flaming, but this will only be able to exist at that opening and not throughout the attic because there is no increase in airflow throughout the attic. When several openings or a very large opening is made through the ceiling below, more mixing will occur, and the fire may begin to grow rapidly, overwhelming any natural or firefighter-made openings in the roof. This creates the potential for the fire to burn downward or for a pulse of hot, unburned gases that mix with air below and ignite

Tactical Consideration # 5

Closely time or limit vertical ventilation until water is in the attic. In the absence of suppression, the positive effect of a roof opening is a very short-lived phenomenon. The accelerating fire will quickly overwhelm all openings and push back into the occupied space.

The fire dynamics changed significantly when a hole in the roof was created. In some of the experiments, a four-foot by four-foot hole was opened over the center of the attic. This simulated a vertical vent performed by the fire service, burn through of the sheathing by the fire, or failure of a skylight. 

Once the hole was opened, the products of combustion exited efficiently, and a large volume of replacement air entered the attic through the eaves, gable vents, a hole in the ceiling, or combinations of all three. This affected the ventilation-limited fire, rapidly increasing the heat release rate. 

Tactical Consideration # 6 

Plastic ridge vents can affect size-up and fire dynamics. As the vents heat, the plastic melts and collapses on the opening at the peak, creating a very effective seal. Once the ridge vent seals, the eaves will act as both the source of air as well as the exhaust, and you may notice a pulsing of smoke out of the eaves.

Tactical Consideration # 7

Wetting sheathing with an eave attack slows attic fire growth. If crews wet the sheathing, either as part of an offensive fire attack or defensively to slow fire spread to uninvolved sections of the structure, the major flame spread mechanism in the attic is eliminated until the moisture evaporates. Removing the soffit and flowing water along the eave line of these structures was the most effective way to gain the upper hand on a fire that was venting through the roof.

Tactical Consideration # 8

Attic construction affects hose stream penetration. The most effective water application takes into consideration the construction of the attic, using the natural channels created by the rafters or trusses to direct the water onto the vast majority of the surfaces.

Tactical Consideration # 9

Consider flowing up instead of down with a master stream. Consider using an aerial device or portable ladders and handlines to open the eaves and flow water into the attic. This approach could result in controlling the fire enough to permit firefighting crews to transition back inside the structure to complete searches, suppression, and overhaul.

Tactical Consideration # 10

Knee wall fire dynamics: During a structure fire, it is possible for fire to enter void spaces and surround crews conducting interior operations. Even though there is a delay between making the breach and the change in conditions, once initiated, the transition to untenable conditions in operation occurs in seconds. Any penetration into the void space from the interior creates a flow path, allowing fire to spread into the interior and exposing crews. This may not happen immediately; therefore, it can occur behind the advancing crew, blocking their egress. 

Tactical Consideration # 11 

Apply water on a knee wall fire at the source and toward the direction of spread before committing to the attic. Applying water using the same path the fire took to enter the void space may be the most effective method at slowing fire growth. Water application to the knee wall will not be effective until the source below it is controlled with direct water application to the source.

Tactical Consideration # 12

Interior operations on knee walls: Tests have demonstrated that the most effective way to get a handle on knee wall fires is to control the source fire; cool the gases prior to making large breaches in the barrier; and then aggressively open the knee walls to complete extinguishment, focusing on wetting the underside of the roof decking.

We’ve all heard that the success of the first hoseline will determine the outcome of the fire. Getting water onto the base of the fire as quickly as possible should be our goal even when it’s in the attic. Consider property conservation. Look at what is actually burning in the attic and get EFFECTIVE water onto what is burning.

REFERENCES

UL-FSRI Attic Fire Main Page - https://ulfirefightersafety.org/research-projects/residential-attic-fire-mitigation-tactics-and-exterior-fire-spread-hazards.html

Technical Report - https://ulfirefightersafety.org/assets/Attic-Final-Report-Online-3b66bed8242c8ee45296ca927ee64237aea73fa21baed433837e3de2fa1b2712.pdf

Fire Service Report - https://ulfirefightersafety.org/assets/Attic-Final-Report-Online-3b66bed8242c8ee45296ca927ee64237aea73fa21baed433837e3de2fa1b2712.pdf

On-line training module - http://cache.learnshare.com/lscdn08092017343257432/courses/170/631403/AtticFires/story.html?

 

SEAN GRAY, a 25-year veteran of the fire service, is a lieutenant with Cobb County (GA) Fire and Emergency Services. He has been a member of multiple technical panels involving firefighting safety research and is an appointed member of the Underwriters Laboratories Firefighter Safety Research Institute advisory board. He coauthored a DVD and the book  The Evolving Fireground: Evidence-Based Tactics (Fire Engineering). He has a bachelor’s degree in fire safety engineering and is an integral part of implementing research-based tactics into the department’s training and daily operations.

P.J. NORWOOD is a deputy chief training officer for the East Haven (CT) Fire Department. He is an FDIC International classroom, workshop, and H.O.T. instructor; a member of the Fire Engineering Educational Advisory Board; a Fire Engineering book and video author; and a former member of the Underwriters Laboratories Technical Panel for Residential Attic Fire Mitigation Tactics and Exterior Fire Spread. He had served four years with the Connecticut Army National Guard. He is a Fire Engineering author and a member of the FDIC International advisory board. He hosts a monthly Fire Engineering blog talk radio and Google hangout. He is certified to the instructor II, officer III, and paramedic levels.

 

Pennwell