Positive pressure ventilation techniques demonstration
Underwriters Laboratories (UL)
Firefighter Safety Institute has been conducting a three-year study titled “Study of the Effectiveness of Fire Service Positive Pressure Ventilation During Fire Attack in Single Family Homes Incorporating Modern Construction Practices.” The purpose of the study is to increase firefighter safety by providing the fire service with credible scientific information, developed from full-scale fire testing in representative modern single-family homes, on the usage of positive pressure ventilation (PPV) fans during fire attack. Twentysix members of The Northern Illinois Chapter of ASHI, along with firefighter staff from neighboring communities and across the country, attended a portion of these experiments on Tuesday, February 03, 2015.
These research studies are conducted in UL’s Large Fire Laboratory on the UL Campus in Northbrook, IL. The benefits of properly applied positive pressure ventilation, as we learned, is to control the positioning of the smoke, heat and deadly gases produced by residential fires to, first of all, better protect any occupants who may still be in the structure and secondly, to allow firefighters quicker access to the source of the fire, allowing them to extinguish the fire sooner to minimize hazard risk to the firefighters themselves.
There were two fire experiments produced February 03, 2015. Experiment 7 was conducted in the morning, followed by experiment 11 in the afternoon. Sensors measuring interior structure temperatures and various toxic gas levels at various height positions throughout the structure, along with interior surveillance cameras, were utilized. There were monitors in the observation room upstairs so that interior structure conditions could be witnessed before the effects were seen from the exterior of the structure.
We were allowed access to the structure both before and after each burn to see the before and after conditions of the interior of the structure. This indoor testing arena has massive filtration exhaust systems, which allows for rapid air clearance with no toxic exhaust to the exterior environment. It was impressive that the smell of scorched structure materials was barely apparent. Each experiment was followed by a discussion forum led by Stephen Kerber, PE, Director, UL Firefighter Safety Research Institute and his staff, NICASHI members and various firefighters from local communities and municipalities across the country.
Experiment outlines were posted as the following example:
Experiment Number 11 Description:
A room and contents fire in bedroom 2 of the single-story structure intended to evaluate the effect of a large number of exhaust points on the effectiveness of positive pressure attack. The front door is the inlet air, the windows of bedroom 2, 3 and the master bedroom are the exhaust points. The bedroom 2, bedroom 3 and master bedroom windows are ventilated by fire department personnel. Suppression occurs via an interior straight stream from the living room into bedroom 2 off the ceiling
Experiment 11 Timeline: Minutes:Seconds
Ignition: 0:00, master bedroom window opened: 8:00, bedroom 2 window opened: 8:15, bedroom 3 window opened: 8:30, front door opened: 9:00, PPV fan on: 9:10, straight stream living room into bedroom 2.
- How does-multiple exhaust openings impact fire behavior and survivability during Positive Pressure Attack (PPA)?
- How does an interior attack affect fire conditions?
What we learned was that conventional firefighting tactics have basically been to punch holes in the structure from the exterior, or from limited interior access to flood water into the home first in an attempt to gain control over the fire before further entry by firefighters. These experiments have taught firefighters that if you can safely access the interior and sweep the source of the fire directly, e.g., the underside of a roof structure decking, the fire is extinguished much more rapidly because the source of the fire is being attacked directly and is more completely extinguished.
The importance of structure ventilation was also discussed. When it comes to saving lives and minimizing structural damage during house fires, it is common and understood that occupants can easily be panicked and as a result, people most likely are not aware of simple measures that can be taken that can make a difference between life and death as well as minimizing structural damage.
When a structural fire in modern light-weight construction with structural components and furnishings that are derived from petroleum products occurs, the average new construction, if allowed enough ventilation, can flash over and become completely involved in as little as 8 minutes. Considering it takes on average 2-4 minutes for 911 to be dispatched, the local fire department needs time to react and travel to the fire house (the term used in the firefighter community of the involved residence) and then assess the structure, exterior wind conditions and other factors, every second is critical.
By simply closing as many doors and windows as reasonably possible during egress from the structure, ventilation of the fire is restricted, minimizing the spread of fire and toxic smoke and gases.
If trapped in the structure, having as many closed doors between occupants and the fire provides the best chances of survivability. The above scenario is also why the firefighter community strives to petition municipalities across the country regarding the importance of residential sprinkler fire suppression systems in modern light-weight construction. On January 19, 2013, NICASHI invited Peg Paul on behalf of The Home Fire Sprinkler Coalition (HFSC) in Frankfort, Illinois, to present to their chapter meeting important statistical data and the importance of the installation of these systems. For further information, their website is www.homefiresprinkler.org. I contacted HFSC after the chapter presentation and requested that I be sent informational packets explaining the operation and maintenance of residential fire sprinkler systems. It is a very nice packet that comes with a laminated header card and zip tie to attach to the main header pipe of the system explaining the use and maintenance of the system, a tri-fold information brochure and even a very informative DVD. The packets come in a 9" by 12" Tyvek envelope. I keep a couple at a time in my service vehicle and when I run across homes with residential fire sprinkler systems installed, I strap the informative header card to the system’s main valve pipe and give my client(s) the balance of the packet. These are available at no cost and clients really appreciate the information.
Height placement of carbon monoxide detectors is not as crucial as smoke detector placement, as studies show that as carbon monoxide levels build in a room, they build evenly from top to bottom. However, when it comes to smoke detectors, it is important that they be ceiling-mounted and not just mounted high on a wall. As fire and smoke spread, it hits the ceiling first, then spreads across the ceiling before filling the room from the top down. Further, placement according to manufacturer’s instructions in close proximity to all sleeping areas, as well as coverage, as needed, on all levels of both Ionic and Electronic Eye technology smoke detectors, has been proven by various studies to provide the earliest possible warning for occupants of the residence. Interconnected smoke detectors can further provide earliest warning because all alarms throughout the residence will alarm as opposed to an independent alarm that may not be heard under certain conditions such as loud audio, sleeping behind closed doors and other conditions.
Further, we learned that when it comes to the fire resistance of various sources of gypsum board, not all gypsum board is of equal fire-resistance. Proper installation of fire resistant assemblies is important as well. The following link provides a PDF document guide produced by U.S. Gypsum for ASTM and UL standards for various fire-resistant assemblies: usg-fire-resistant-assemblies-catalog-en-SA100
As home inspectors, we all believe in the importance of educating consumers about their options when investing in safe housing and components for their families. Keep in mind that in various municipalities across the country where ordinances in these matters are perhaps based more on affordability of housing as opposed to the safety of their residents, human life is occasionally sacrificed. Our hope is to educate consumers as much as we can to avoid such tragedy. I hope you have found this article and the linked resources useful in your ongoing care and concern for your clients and public safety.