Finding the effective wetting agent

CarolinaFireJournal -

04/29/2011 -
When wildfire threatens residential areas, homeowners do whatever they can to protect their property. One response is to apply wetting agents to their houses, but the effectiveness of such agents has been an uncertain matter of opinion. To bring some engineering and science to the question, researchers from the Lee College of Engineering’s Fire Safety Engineering Technology program have been leading a three-year comprehensive study of wetting agents. image

The project is sponsored by the Federal Emergency Management Agency of the Department of Homeland Security for about $500,000. The research team includes four Engineering Technology Fire Safety faculty members, two graduate students and two undergraduate students.

“There is a history of people and firefighters wetting homes and vegetation as fire approaches in hopes of saving structures,” said Dr. Jozef Urbas, associate professor of Fire Safety, and the project’s principal investigator. “There is no real data on the effectiveness of wetting agents in wildland urban fire conditions, though. We are trying to quantify the effectiveness of water, foam and gel, and see what good they do.”


A fire retardent gel applied to test wall.

In the first year of the project, the team performed intermediate-scale laboratory tests. Using an intermediate-scale calorimeter to determine critical flux for ignition (the heat radiation required to ignite material with a pilot flame present) they tested more than 500 samples. Testing was done on 10 types of intermediate size landscaping plants, three types of exterior wall material, and three types of roofing material on 1 m x 1 m specimens. Each of the items was tested with the three agents - water, foam and gel. The agents were tested immediately after application and one hour after application. Other variables included subjecting the samples to intense sunlight and wind.

The second year of the project was to verify the lab results in full-scale fire tests.

“Fire behavior is very difficult to accurately mimic in small-scale lab settings,” Dr. Urbas said. “We were confident in the methods we had developed for the lab tests, but still had to verify our results with full-scale tests.”

At its research facility at the Charlotte Fire Training Academy and with the help of the Charlotte Fire Department, the team performed six tests of different wall and roofing materials. They tested the materials with only water and gel applications, because the foam had been determined to have similar effectiveness as water.


Pictured back row (l-r):Dave Murphy, Dustin Reynolds, Lana Nelson, Richie Bingler, Joe Urbas & Ellen Sogolow. Front row (l-r): Aixi Zhou, Jeff Kimble, Robbie Myers & Palak Desai.

In the full-scale tests, the team instrumented the walls and roof structures with heat flux gauges, and measured temperature in number of places with thermocouples. They then burned stacks of wood pallets at various distances from the structures to generate the fire and heat radiation needed. The heat fluxes and temperatures on walls and roofs were measured constantly with the data acquisition equipment, and the tests were also videotaped.

“The full-scale tests were very successful in verifying the intermediate-scale lab results,” Dr. Urbas said.

The tests results have shown that the most effective wetting agent is the gel. It is the only wetting agent effective when applied one hour before the fire reaches the structure when exposed to intense sun and wind during that time period.

For the final year of the project, the team has started the process of developing their intermediate-scale test method into a full American Standardization and Testing of Materials (ASTM) standard test method. It will also develop an education module for firefighters that will instruct them in the optimum ways of using wetting agents.

The project has been very successful, Dr. Urbas said, and much of the success can be attributed to the great working relationship between the UNC Charlotte researchers and the Charlotte Fire Department. “I especially want to recognize Chief Kevin Gordon and Captain Robbie Myers, who helped with all elements of the large-scale tests,” Dr. Urbas said. “The whole fire department has been great in helping and doing whatever they could for us.”



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