By Steve Kerber and Todd Harms
Published Sunday, April 1, 2012
| From the April 2012 Issue of FireRescue
The window of time in which to operate offensively on the modern fireground is compressed, and conditions change rapidly. With today’s modern furnishings made up of primarily synthetic materials, fire growth and fire spread is now faster than ever. Tactical support operations under these conditions are tasks that assist interior offensive companies during search and rescue and fire control functions (forcible entry, ventilation and access to concealed spaces).
Ventilation has proven vital to these offensive firefights. We ventilate the fire building to improve interior tenability for firefighters and possible victims, improve interior visibility, and channel the heat and smoke up and out of the structure.
Ventilation must be coordinated with interior crews in a timely manner. The best-timed and most efficient release of heat and smoke out of the building ensures safer operating positions for interior firefighters. A recent UL experiment using vertical ventilation made the fire much bigger much faster. If water was introduced quickly, the fire would have darkened down and the steam and heat would have lifted, making conditions immediately more tenable. If water was not ready, and there was a search crew inside, that crew would likely have been jumping out of the windows. It’s all about the timing.
That’s why, as much as we stress ventilation’s role in offensive fire attack, it’s important to remember that incorrectly applied, it can make conditions unsafe for firefighters. Venting does not always equal cooling.
In this article, we will take a closer look at how our understanding of ventilation is changing even as it remains key to offensive attacks on the modern fireground.
Due to the increase in synthetic materials and lightweight construction, we believe that a reconsideration of traditional assumptions regarding vertical ventilation could lead to major improvements in firefighter safety and operational outcomes. Key questions that need answers include:
- What is the proper size of a ventilation hole to achieve effective ventilation?
- What are the effects of different size ventilation openings?
- Does interior visibility and heat reduction change as the ventilation opening is increased?
- As the layout of the structure changes (one-story vs. a two-story residential occupancy), should ventilation tactics change as well?
- Do we always need to ventilate directly over the fire? Can ventilating away from the fire (in a safer position on the roof) still have a positive impact on the interior environment?
- What effect does an open door or window have on the interior environment?
- What role does timing play on ventilation?
UL recently embarked on a study of vertical ventilation that will help answer these questions. This type of research is key as it can be immediately and directly applied to everyday fireground operations, leading to improved firefighter safety.
But we must be prepared for the results of such research to challenge our traditional tactics. Many departments have standard operating procedures (SOPs) with regard to vertical ventilation. These procedures have been developed throughout the years based upon the experiences passed on from generation to generation. Although these procedures continue to be very successful, they have never been fully or formally assessed from a scientific perspective. Just because something has been done for many years does not mean it is correct; it also doesn’t mean it’s incorrect, but new scientific information can help us understand why it’s right or wrong, and under what circumstances. The fire environment has changed; some tactics and training practices may need to as well, to keep firefighters up to date and safe.
To illustrate this, let’s take a look at the current ventilation SOPs of the Phoenix Fire Department (PFD).
Roof Sector Operations
In the PFD ventilation SOPs, we state:
- “Adequate-size ventilation holes must be cut and opened if ventilation is to be successful. Ventilation hole(s) of at least 10% of roof surface of the involved area is a rule of thumb to consider.”
- “When you cut a hole in a roof, cut a big one.”
- “Vertical ventilation, as close to directly over the fire as possible, is the most effective form of ventilation in working interior fire situations.”
Ventilation can be accomplished through vertical, horizontal, mechanical and/or hydraulic actions. In the PFD, these support functions are generally accomplished by either a ladder company or squad company. On residential fires, we dispatch an initial assignment of three engine companies, a ladder company, a squad company (if they’re located within five miles), an ambulance and two battalion chiefs. A tactical benchmark for command is the early assignment of vertical ventilation, which, when coordinated with fire attack, optimizes firefighter safety and effective overall fireground operations.
The initial ladder or squad arriving on scene is usually assigned to the roof sector. The objectives for roof sector operations include:
Initial and ongoing size-up
The size-up of the structure should take into account the following critical fireground factors:
- The building: Consider the size and the layout of the structure (small, medium or large; one story or two, etc.). Estimate the age of the building in order to predict basic construction features. Is the structure lightweight or conventional construction? What are the interior arrangements? Where is the garage? Does the structure have open vaulted ceilings? Does it have a middle hallway? What type of roof does the building have and how will the construction of this roof affect ventilation? (Note: Currently we do not allow vertical ventilation on tile roofs, but we are evaluating a new SOP for this.) Consider the access and egress from the structure through windows and doors. Finally, does the building exhibit features that will prevent vertical ventilation?
- The fire: What’s burning? Is it a contents fire or is it structural? For command size-up, all fires should be assumed structural until confirmed by crews that the fire has not extended. Estimate what percentage of the structure is involved in fire—5%, 15%, 25%? Where is the fire traveling and how will ventilation assist in slowing the extension? What is the stage of the fire and where are the initial engine company’s handlines positioned? Ventilation should not be attempted for first-floor fires in a multi-story structure, fires that have extended well beyond the room of origin and/or advanced “structure” fires.
- Life hazard: What is rescue profile and survivability of any occupants? Where are they located, how many people and what is their condition, if known? (See sidebar, below.)
- Type of occupancy: What is the fire load of the occupancy? Are there any special hazards (e.g., hazardous and/or flammable/combustible contents) that crews need to be aware of?
- Exterior arrangements: Are all four sides of the exterior accessible? Are there any exposures or barriers for apparatus positioning?
- Fireground actions: What is the status of the operation when the ladder or squad arrives? Where have the initial engine companies deployed? To coordinate ventilation, the interior crew should use a CAN (conditions-actions-needs) report to advise command of their location, their actions and what they need. Once the ceiling is punched through, the heat and gases begin to rise and the engine crew can begin to put water on the fire.
- Special circumstances: The season, weather, wind direction and speed, the time of day and any special hazards can all affect the decision whether to ventilate and how. For more information on the impact of wind on fires, see www.nist.gov/fire/wdf.cfm.
Once the initial size-up has been completed, the ladder or squad company will determine a safe working surface on the roof by sounding it with a flat-head axe, a pike pole or a special stamping tool developed by PFD crews. Factors to consider include the location and movement of the fire, whether the fire has extended to the attic, the effect the fire has had on the roof, and whether there are any dead loads affecting the roof structure.
The next steps happen in quick succession.
1. Complete an adequately sized ventilation opening to achieve effective ventilation. Note: PFD crews cut at least a 4 x 4 or 4 x 8 hole, but we hope to have more information about the ideal opening size following the completion of the current UL studies. Consider:
- Ventilation opening size (currently, we aim for 10% of the involved space)
- The smoke volume, speed and pressure
- Wind direction, speed and effects on ventilation
- Ventilation completed toward the top of pitched roofs
2. Coordinate roof ventilation with interior crews
- Roof and interior crews should communicate about the fire’s location.
- Interior crews should communicate the effect ventilation has on interior conditions.
- Interior and roof crews should then assess the need for additional ventilation.
3. Coordinate roof and fire control operations as directed by command.
- Handlines may be used for exposure protection.
- During offensive attack, handlines should not be operated into a ventilation hole. Anytime water is applied into a ventilation hole, it must be coordinated with other fireground actions.
4. Maintain rooftop monitoring of the structure and fire conditions. (Note: In some cases, this can be done from the ground. If it’s not necessary for you to be on the roof, get down.)
- Monitor the ventilation opening. You will likely see fire as the smoke vents (rich, heated smoke mixes with O2 upon exiting, and immediately ignites), but this doesn’t necessarily mean conditions are deteriorating. If fire continues to exit through the hole, command must immediately check on the status of interior crews to determine if they’ve been able to put water on the fire.
- Watch for deteriorating structural conditions of the roof.
5. Communicate progress reports to command, including information on:
- Roof conditions
- Ventilation status (smoke vs. fire)
- Improving vs. deteriorating conditions
Safety Is Paramount
Roof positions are one of the most dangerous assignments on the fireground. Over the past few years, the PFD has had a number of close calls directly related to vertical ventilation activities. On one such recent instance, a firefighter from a ladder company fell through the roof and attic to the fire room below. Fortunately, he escaped without injury. This example reiterates the fact that the company and the company officer must constantly reevaluate the roof conditions and look for visual changes in the fire activity working below the roof.
Such near-misses also underscore that the potential gain from such an operation must outweigh the risk. Roof operations shouldn’t be carried out automatically, a result of a riding position. Company officers must ensure that members assigned to roof operations know that they will only go to the roof after appropriate size-up and determination that vertical ventilation will be effective and is worth the risks. Roof firefighters should also be clear on alternative tasks that will be assigned to them if roof operations are not conducive to the current fireground conditions. Remember: Firefighters are action-oriented. Giving roof firefighters alternative responsibilities can reduce the possibility they will go to the roof simply because they feel that they aren’t doing their job if they don’t.
For safe roof operations, the crew must access the roof from a safe location, properly sound and transverse the roof to the cutting location, have a plan for a secondary means of escape if necessary, and follow SOPs for each assigned task of the ventilation crew.
UL’s Vertical Ventilation Study
Through a Department of Homeland Security Assistance to Firefighter Grant, UL has begun to examine the impact of vertical ventilation on fireground operations.
The study examines vertical ventilation techniques on one- and two-story residences. Two test houses have been constructed in the fire test facility at UL’s head office in Northbrook, Ill. The first house is a one-story, 1,200-square-foot, three-bedroom, one-bathroom home. The second house is a two-story, 3,200-square-foot, four-bedroom, two-and-one-half-bathroom home. This house features a modern open floor plan, two-story great room and open foyer. Seventeen experiments will be conducted with varying ventilation locations.
Objectives for the project include:
- Improve firefighter safety by increasing knowledge of fire behavior.
- Develop knowledge of vertical ventilation tactics.
- Generate understanding of modern construction practices—such as open floor plans and emerging attic construction design—on fire growth.
- Address concerns about smoke alarm technologies and placement to support fire department smoke alarm distribution programs.
- Develop tactical considerations based on the experimental results that can be incorporated into firefighting SOPs.
- Examine the impact of applying external hose teams as part of transitional attack tactics.
In January, the first set of experiments were conducted in both the one- and two-story residential buildings (see photos). These included:
- The coordination of an open front door and a window near the fire during ventilation.
- A 4' x 4' vent hole above the fire with a 4" front door opening.
- A 4' x 4' vent hole above the fire with an open front door.
- A 4' x 8' vent hole above the fire.
- A 4' x 4' vent hole remote from the fire.
Temperatures, pressures, gas concentrations and video views were monitored in every room of each house during the experiments. These measurements will be analyzed to determine the impact of each of the different ventilation scenarios on potential occupant and firefighter locations. A meeting of the project’s technical panel, consisting of fire department representatives from across the country, will examine the results and develop tactical considerations that will be included in the final report and online training program. By the end of the year, UL will develop an interactive online training program geared toward the fire service and offered free of charge at www.ul.com/fireservice.
A Final Word
Vertical ventilation has always played an important role on the fireground, and it will continue to do so. However, current research promises to change the way we think about ventilation and will necessitate changes in tactics and SOPs. We no longer have to presume how venting will affect fire behavior and interior conditions; we have the means to scientifically prove it, adjust our tactics accordingly and get the word out to the fire service as a whole. The results of these experiments will no doubt challenge some long-held positions on ventilation, and in some cases may seem counterintuitive. But we must be open-minded and willing to embrace scientifically proven tactics. We owe it to every firefighter who goes up on a roof.
Sidebar: Creating a Rescue Profile
Most fireground rescues for the Phoenix Fire Department (PFD) occur in single-family homes or multi-family apartment buildings. The policy of the PFD is to extend a primary and secondary search during all offensive fires. In residential fires with a rescue, we usually pull out one or two victims. On occasion, we’re confronted with a rescue situation involving an entire family.
The priority is searching the area closest to the fire, then the remaining structure. During night-time hours, the bedrooms and the normal access and egress are always a priority. Most people try to exit a building the way they came in and are often found near the front door. Fire victims usually die from smoke inhalation and carbon monoxide poisoning, not burns. If doors are closed and smoke and heat is kept out of the bedrooms, the chances for survival are greatly increased.
Upon arriving on scene, the following life safety factors must be considered:
- The number of possible occupants. Is this a single-family residence, an apartment complex or a large nursing home? Do we have anybody on scene reporting trapped occupants? If so, where were they last seen?
- Where could the occupants be located in relation to the fire? Is the fire in the living room, the garage, the bedroom?
- What points of access do firefighters have to victims (doors, hallways, windows, etc.)?
- What stage is the fire in? What percentage of the structure is involved and what are the smoke and fire conditions? Where is the fire, what’s the layout, can I get in, do I have a second way out, where am I going once I make the interior?
- What resources will it take to extinguish the fire and stop extension?
- What is the condition of occupants (by virtue of fire exposure)? Are they visible from a window or out on a balcony?
- What resources do I have to commit for the initial search and rescue operations?
- What are the EMS needs?
- What risk are we going to take with firefighters?
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