House Fire training structure on fire

Attic Fire Experiments - Northbrook, IL

January 15, 2014

As part of the 2012 DHS Grant to study “Residential Attic Fire Mitigation Tactics and Exterior Fire Spread Hazards on Fire Fighter Safety'' (Attic & Exterior Fires), testing involving four, full-scale attics with an 8’ space below was conducted in UL’s large fire lab in Northbrook, IL. Each test was designed to evaluate the effectiveness of one or more fire suppression tactics. The tests were conducted over two and a half weeks including setup and tear down resulting in tens of thousands of data points, hours of video and thousands of still images.

The test set up was a 30’ by 36’ wood frame structure with a truss roof system, plywood sheathing, ridge vent, gable vents and eave vents. The attic was separated from the space below with a layer of ½” gypsum wall board and two layers of 6” fiberglass batt insulation. Attic access hatches measuring 2’ by 4’ were used to gain access to the attic space for instrumentation however were closed off with a ½” piece of gypsum wall board and no insulation during tests. The space below was finished with ½” gypsum wall board to provide an enclosure finished with tape and plaster. A single door provided access for suppression tactics and instrumentation. Four test setups were used to conduct a total of seven tactics.

Instrumentation was provided to measure temperature of the gasses in the attic and space below, heat flux from the gable vents, velocity of gasses from the gable vents and velocity of gasses in through the front door. In eave tests the velocity was measured in through the eave vents. Video footage of the tactic being performed, attic space, interior space and exterior were recorded for each test.

Analyzing the data and video from the four days of testing will take some time, however below we’ve provided a description of the 7 tactics tested along with a short video demonstrating the tactic being performed with accompanied by an overall view of the test set up. The Technical Panel for this project will be meeting spring of 2014 to review all the data/video and develop tactical considerations for the final report.

Tactic 1 – Fog from Below, Ventilated Attic Fog Attack

The first tactic tested was intended to test the ability of a fog stream to suppress a ventilated attic fire. The fire was started in the center of the attic and permitted to grow until fire was visible from the ridge line and gable vents. A simulated engine crew with a combination nozzle set to fog and supplied with 100psi (150 gpm) entered just inside the front door, hooked a small (approximately 6”-8”) hole, pushed the insulation out of the way and flowed water for 40 seconds. At that time the line was shut down and the crew backed out to see the impact. The tactic and impact can be seen in the short video here.

Tactic 2 – Large Hole, Fog & Straight Stream below, Un-ventilated Attic Large Hole Unvented

This tactic was designed to evaluate the impact of a larger opening below the fire. Crews entered just inside the front door and hooked a section of ceiling approximately 8’ x 8’. The impact of the ventilation opening on the fire conditions was evaluated. After conditions stabilized crews using the same nozzle from tactic 1 applied 5 seconds a straight stream followed immediately by 5 seconds of fog. The crew then exited the structure and the conditions were evaluated. A video of this tactic can be seen here.

Tactic 3 – Large Hole, Fog & Straight Stream below, Ventilated Attic Large Hole

To evaluate further the effect of ventilation on attic fire dynamics the test from tactic 2 was extended by ventilating an approximately 4’ x 4’ hole on the rear of the attic. The fire was permitted to grow to flashover conditions with the existing 8’ x 8’ hole below. After the attic was involved in flames the crew entered just inside the front door and applied water from below. The same nozzle was utilized as before with a fog stream being directed various angles in through the 8’ x 8’ hole. A video of this tactic can be seen here.

Tactic 4 – Gable Attack, Straight Stream, Un-ventilated Attic Gable Attack Unvented

As many structures have gable vents to allow for proper air flow in the attic during non-fire situations the next tactic was designed to take advantage of this existing opening for fire attack. A fire was ignited at the center of the attic and permitted to grow until it reached under-ventilated conditions. A simulated engine company then applied water using an automatic nozzle set on straight stream for 20 seconds at various angles attempting to place water as deep into the attic as possible. The gable vents used were plastic vents which melted away early in the test. A video of this tactic can be found here.

Tactic 5 – Gable Attack, Straight Stream, Ventilated Attic Gable Attack Vented

The test fire from tactic 4 was again used to evaluate the effectiveness of a gable end attack on an attic which had been ventilated and permitted to reach flash over conditions within the attic space. The simulated engine crew applied water from the gable. A short clip of this tactic can be found here.

Tactic 6 – Eave Attack, Un-vented Attic Eave Attack Unvented

Attempting to use the natural ventilation points in the attic again the tactic of applying water through the eave vents was evaluated in an unventilated attic. The fire was started in the center of the attic and permitted to grow to under-ventilated conditions. The eaves were pulled using a trash hook and conditions were evaluated as the fire began to starve itself for oxygen. Water was applied using an automatic nozzle on straight stream from the eaves upward toward the peak. The water was applied to each truss bay accessible from the front side of the structure. After application the conditions were reviewed to determine the impact of water application. A video of this tactic can be found here.

Tactic 7 – Eave Attack, Vented Attic Eave Attack Vented

To continue with the evaluation of both ventilated and unventilated attics the eave attack was employed after the attic had been ventilated. The fire was started on the right side of the attic and permitted to grow until the attic reached flash over conditions. The water application technique used in tactic 6 above was employed on the vented attic. The tactic and its effects can be seen in a short video located here.

Attic Fire ISO drawing rendering
Residential Attic Fire Mitigation Tactics and Exterior Fire Spread Hazards on Firefighter Safety