A Closer Look at the UL Ventilation Study

New fire behavior and ventilation study sheds light on outdated tactics

By Jane Jerrard
Published Sunday, May 1, 2011 | From the May 2011 Issue of FireRescue

You may think the one constant in our industry is fire behavior—but fighting residential fires with the same tactics used a generation ago is no longer safe, as proved by a study recently released by Underwriters Laboratories (UL).

Research conducted in UL’s Northbrook, Ill., facilities examined fire service ventilation practices, combined with fire behavior involving modern home construction and furnishings. The UL study reports “a steady change in the residential fire environment over the past several decades.”

Asked what the fire service should learn from the study, lead researcher Stephen Kerber replies, “I’d say the one thing they should probably take away is a better understanding of fire behavior, especially with today’s houses, and a better coordination of their ventilation.”

Fresh Air
The study proved something many firefighters already know firsthand: The practice of ventilating—or even forcing entry—will speed up the fire. Ventilation, combined with highly flammable modern materials, is resulting in much faster-burning fires. How fast? The UL research demonstrated: “Taking the average time for every experiment from the time of ventilation to the time of the onset of firefighter untenability, conditions yield 100 seconds for [a] one-story house and 200 seconds for [a] two-story house. In many of the experiments, from the onset of firefighter untenability until flashover was less than 10 seconds. These times should be treated as being very conservative.”

Timothy E. Sendelbach, editor-in-chief of FireRescue magazine, notes: “To some degree, it tells us the obvious, but it asks us to stop doing what we do. What I took away from the study is that we’ve got to be more considerate about door control. That open door also feeds the fire—even as we enter the building and move toward it.”

New vs. Old
The other major finding of the UL study was revealing the difference between modern homes and homes of the past. UL constructed two homes—one a single-story, 1,200-square-foot, eight-room house, and the other a two-story, 3,200-square-foot, 12-room house—and then conducted 15 experiments with ventilation locations and the number of ventilation openings.

Kerber explains, “Most things in houses today are synthetic; this hasn’t been a fast change, but the fire service hasn’t revisited its tactics for a generation.” And of course, changes in furnishings and residences will continue. “This research definitely needs to be revisited in 5–10 years.”

Ed Hartin, chief of Whidbey Island (Wash.) Fire & Rescue and an editorial board member of FireRescue magazine, was impressed with the difference in flashover points between the older home and the modern one. “With legacy furniture, it was a slow-developing fire—this is the type of fire my father would have fought,” he says. “But with modern furniture, the fire burned much more quickly and became ventilation-limited.” Forty years ago, firefighters could open windows to introduce ventilation and cool the fire. Today, Hartin says, “with quicker-burning fires, this is no longer true.”

UL’s three-minute video (www.ul.com/global/eng/pages/offerings/industries/buildingmaterials/fire/fireservice/ventilation/) shows what happens to a modern room and a “legacy” room, when a lit candle is placed on the sofa of each. The fire in the legacy room takes 29 minutes, 25 seconds to reach flashover; the fire in the modern room takes just 3 minutes and 40 seconds. “That should be the kidney punch that makes firefighters really pay attention,” Sendelbach says.

Lessons to Be Learned
The fire service needs to pay attention to this research, and change the way firefighters think and act when approaching a residential fire.

“First of all, we need to recognize that most fires by their incipient stage are limited-ventilation fires. Anything we do to ventilate will make that fire bigger,” Hartin points out. “I’m not saying don’t ventilate—but we shouldn’t be surprised by the result. Responders should pretty much be ready to put water on the fire when we ventilate.” He continues, “Secondly, there needs to be coordination between fire attack and ventilation. The people assigned to those tasks really need to communicate closely with each other.”

Take the Online Course
UL has made it easy for individual firefighters and departments to learn the facts and tactical considerations by creating a free online training program. Kerber explains, “As part of the grant deliverable, we have to write a technical report. No firefighter is going to read a 400-page report, so we created an online course they can take. It’s video-based, they can go at their own pace, and they can stop at any point and come back later.”

The course, “Impact of Ventilation on Fire Behavior in Legacy and Contemporary Residential Construction,” is available at http://content.learnshare.com/courses/73/306714/player.html.

Hartin says, “I’m beating the drum and saying every firefighter on the planet should complete that course.” In fact, his department created a multiple-choice test to accompany the course, and is putting every firefighter through it. “A number of our firefighters have already remarked, ‘That’s different from what they taught me in recruit school,’” Hartin says. “We’ve been seeing this for years and years on the fireground, but people aren’t seeing the connection between ventilation and fire growth—or they’ve never determined what that connection means.”

A Final Word
Everything changes—even fire. Fire departments need to change their tactics to keep up with new developments and ensure the safety of their members. As Hartin points out, “Fire axioms are passed down generation by generation in the fire service—but things have changed.”


6 More Tactical Recommendations
In addition to the recommendations mentioned in this article, consider these tactical recommendations arising from the UL research:

1. Expect a decay period: Because the stages of fire development change when a fire becomes ventilation-limited, it is now common to have a decay period prior to flashover, which emphasizes the importance of ventilation.
2. Watch for lack of smoke: UL experiments showed that once a fire became ventilation-limited, the smoke being forced out of gaps of the houses greatly diminished or stopped. A lack of evident smoke during size-up should trigger awareness of potential conditions inside.
3. Be prepared when you enter: Once the front door is opened, attention should be given to the flow through the front door. A rapid inrush of air or a tunneling effect could indicate a ventilation-limited fire.
4. Close doors during Vent, Enter, Search (VES): During VES, primary importance should be given to closing the door to the room. This eliminates the impact of the open vent, and increases tenability for potential occupants while the smoke ventilates from the now isolated room.
5. Can you vent enough? In experiments where multiple ventilation locations were created, it was not possible to create fuel-limited fires. The fire responded to all additional air provided. That means that even with a ventilation location open, the fire is still ventilation-limited and will respond just as fast or faster to any additional air.  
6. Shut the door: Closing a door between the occupant (including firefighters) and the fire can increase the chance of survivability. When a firefighter becomes separated from their crew and conditions deteriorate, a good choice of action is to go into a room and close the door until the fire is knocked down, or escape out a window with more time provided by the closed door.

Comment Now: Post Your Thoughts & Comments on This Story

UL’s 3-minute video shows a modern room where a lit candle is placed on the sofa. These photos show the room at 3 minutes after ignition. (Photos Courtesy Steve Kerber/Underwriters Laboratories)
This photo shows at 3 minutes and 30 seconds after ignition. (Photos Courtesy Steve Kerber/Underwriters Laboratories)


A Closer Look at the UL Ventilation Study

New fire behavior and ventilation study sheds light on outdated tactics 3 minutes after ignition
UL’s 3-minute video shows a modern room where a lit candle is placed on the sofa. These photos show the room at 3 minutes after ignition. (Photos Courtesy Steve Kerber/Underwriters Laboratories)

3 minutes and 30 seconds after ignition
This photo shows at 3 minutes and 30 seconds after ignition. (Photos Courtesy Steve Kerber/Underwriters Laboratories)

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