Lawrence-Douglas County Fire Medical 207.42 Procedure and Procedures/SOPS/SOP PDF...Lawrence-Douglas County Fire Medical Procedure 207.42 Title: Ventilation Effective Date: Draft Page

Lawrence-Douglas County Fire Medical Procedure 207.42 Title:

Ventilation Effective Date: Draft

Page 1 of 13 Supersedes – SOP

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1 PURPOSE 1

2

To describe guidelines and procedures for controlling ventilation at a structure fire. 3

2 SCOPE 4

Applies to all department members. 5

6

3 ACCREDITATION REFERENCE 7

8

5E 9

10

4 PROCEDURE 11

12

Ventilation considerations are a key component of the Incident Action Plan (IAP) at a structure 13

fire. The tactics used for ventilation will depend on the circumstances of each incident. Since 14

fires are dynamic events, ventilation efforts and their effects must be managed and assessed 15

throughout an incident. 16

This SOP is not intended to describe all possible combinations of tactics, and assignments for 17

ventilation at every possible type of fire. It explains how ventilation will be assigned within the IAP 18

and provides guidelines for ventilation and tactics. 19

20

Ventilation Guidelines 21

22

Ventilation changes a fire’s growth and behavior. When coordinated with fire attack, the right 23

ventilation tactic, at the right time, will protect victims and interior crews, and speed 24

extinguishment with minimum damage to property. 25

By contrast, incorrect ventilation can make the situation much worse. Incorrect ventilation can 26

take many forms. It could be as simple as choosing the wrong tactic for the incident. 27

Horizontal ventilation on the windward side of a structure on a windy day. 28

Positive Pressure Ventilation in a structure without adequate exhaust openings. 29

It could also be performing the correct tactic but at the wrong time. 30

Ventilating before the attack team is in position, allowing the fire time and oxygen to row. 31

Turning in the fan for Positive Pressure Ventilation before the lines are opened up. 32

In all cases, incorrect ventilation can increase the intensity and spread of the fire, increase the 33

risk to firefighters and victims, and increase the damage caused by the fire. 34

If possible, ventilation openings should be controlled – able to be closed again if needed. 35

Breaking glass (while commonly needed) should only be done after ensuring there is not a 36

method of opening a door/window that will allow it to be sealed again. 37

Unless an immediate life hazard is present, firefighters must not break glass or otherwise 38

create openings into the structure without orders from the IC/Fire Attack. Uncoordinated 39

ventilation can dramatically change the fire’s dynamics, endangering firefighters and civilians. 40

Ventilation tactics must be chosen deliberately, after proper size-up, and in conjunction with 41




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the IAP. Firefighters and officers who are assigned to ventilation must understand more than 42

what they are ordered to do, they must know why they are doing it, and what effect they should 43

expect to see if it is working. 44

If a ventilation tactic does not appear to make sense in context of the total firefighting effort, or 45

it might put firefighters or victims in danger, alert the officer or the IC. 46

Likewise, if the fire does not behave as expected after ventilation, notify the IC. 47

In both cases, the information provided allows the IC to adjust strategy/tactics, and protect 48

firefighters from serious injury or death. 49

Ventilation Methods 50

Detailed instructions on every ventilation tactic is beyond the scope of this SOP, which is not a 51

substitute for training, practice, and experience. Instead, this section will provide a broad 52

overview of the most common ventilation tactics. For the purposes of this SOP, Vent-Enter-53

Isolate-Search (VEIS) is considered a Search/Rescue tactic and not covered, except how its 54

use relates to other ventilation tactics. 55

Horizontal Ventilation 56

Horizontal ventilation uses openings in the walls of the structure as exhausts to allow the high-57

pressure smoke and heat from the fire to escape. Typically, these are pre-existing openings in 58

the structure, such as doors or windows 59

60

When creating a horizontal ventilation opening, remove all obstructions (sash, curtains, 61

screens, etc.) from the opening, so it can be used as an emergency egress if conditions 62

deteriorate. 63

64

Horizontal ventilation is typically performed from the exterior, and focused on managing the 65

behavior and growth of a fire. 66

67

68

69

Indications Contraindications Tactical Considerations

Attack lines flowing water into the fire area

Attack lines are reasonably expected to be flowing water into the fire area before the fire can grow after venting

Firefighters or victims operating in the flow path between the fire and the intended vent opening

Backdraft conditions

High winds in the directions of the intended ventilation opening.

The door through which the Fire Attack hand line enters, if left open, is a horizontal ventilation opening.

Exposures close to the intended ventilation opening must be monitored.

The fire can extend to the exterior of the structure, such as the siding or soffit.




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Vertical Ventilation 70

71

Vertical ventilation typically takes longer than horizontal ventilation, and is inherently more 72

hazardous because it requires crews to operate above a fire, often on a pitched surface. 73

When properly performed, the hazards can be minimized and some fires may require this 74

tactic. Therefore, it is essential firefighters are familiar with it and prepared to carry it out. 75

The first step is size-up to determine where the vertical hole will be cut. If the location chosen 76

for ventilation does not have access to the fire area, ventilation will be delayed and the effort 77

wasted, and the hole may draw fire into a previously intact area. Once a location for ventilation 78

is identified, select a landmark to stay oriented while on the roof. This could be a ladder, a 79

tree, or a feature on the roof. 80

A firefighter should make the cuts working from the weak side to the strong side and ensure a 81

path to the escape route remains clear while the Company Officer continuously monitors the 82

roof and fire conditions for changes. 83

Cuts should be no deeper than necessary to remove the roof decking. 84

85

86

Modern building construction and 87

home furnishings will need large 88

openings. In a normal wood frame 89

home, a 4’ x 8’ ventilation hole is 90

standard. The safest and more 91

efficient method to create this 92

opening is the 7-9-8 cut, as shown 93


Horizontal exhaust openings are unavailable

Tactical considerations require a vertical exhaust opening

Pre-existing vertical openings (roof access hatches, skylights, etc.)

Heavy fire in attic/concealed space

Impervious/dangerous roof coverings (tile, concrete, etc.)

Hazardous weather conditions (lightning, snow/ice)

Hazardous building construction (lightweight construction, bow string truss, etc.)

Must be performed above the fire area, which should be determined from size-up

Need 2 routes of egress (ladder, aerial, etc.) off the roof

Minimize number of firefighters involved, and spread out to avoid concentrating weight

Avoid operating around heavy loads (HVAC, etc.)

Cut inspection hole to determine conditions below

Figure 1: Cut pattern for 7-9-8 ventilation hole




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in Figure 1: 94

When the decking is louvered to create a vent opening, crews may need to use long pike 95

poles to break out the ceiling that separates the exhaust opening from the fire area. 96

Firefighters must be cautious not to overbalance when breaking out ceiling below the vent 97

opening. 98

Limited Ventilation, (“Door Control”) 99

100

Limited ventilation, or “Door Control” is based on modern fire science research. Most fires are 101

ventilation-limited by the time firefighters arrive on scene. The act of opening a door and 102

advancing an attack line into structure introduces a great deal of oxygen to the fire. This 103

combines with the heat and fuel already present to greatly increase the extent of the fire and 104

draw it toward attack crew. 105

Firefighters have a 106 very short period of time to begin applying water 107 to the fire before this occurs. A good rule of thumb 108 is they have 100 seconds in a 1-story house, and 109 200 seconds in a 2-story house. 110

Door Control involves 111 intentionally restricting the amount of air that can 112 enter or exit the structure through the fire attack 113 entrance. The simplest method is to have a 114 firefighter assigned to keep the door mostly closed 115 behind the attack crew, and feed them hose 116 around the door. Other methods might involve 117 assigning additional firefighters to push 118 hose around the door, or using a device such 119 as a smoke curtain to block the flow of air into the 120 structure.

If done correctly, this 121 tactic can extend the time available to interior 122 crews to advance to the seat of the fire before it 123 begins rapid growth and interior conditions 124 become untenable 125

126

127

128

129

130

131

132

133

134

135

136

Figure 2: A firefighter performing door

control




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137

Positive Pressure Ventilation 138

Positive Pressure Ventilation (PPV) uses fan(s) to create a pressure gradient in a building that 139

will force smoke out of one or more exhaust openings. When performed correctly, PPV can 140

dramatically improve visibility after knock down, and minimize firefighter and victim exposure to 141

thermal disruption and steam resulting from firefighting efforts. This improves victim 142

survivability and firefighter safety, and expedites completing search operations. 143

For greatest effect, this tactic should be started immediately after interior crews achieve a 144

knock down on the fire. If the IC intends to use this tactic, at least one firefighter should be in 145

position at the doorway, awaiting orders to turn in the fan. That firefighter must remain by the 146

fan, prepared to shut it down until the effectiveness and safety of this tactic is confirmed and 147

he or she is released by the IC or D/G Supervisor. 148


Building layout/content or other incident factors will prevent rapid advancement to the seat of the fire.

Fire has exhausted available oxygen, but high heat and smoke will cause rapid fire growth and expansion with introduction of oxygen.

Thick turbulent black smoke puffing from small openings that has died away prior to application of water – this is a sign that the fire is only waiting for enough oxygen to flare back up rapidly on interior crews.

Door or other openings near the fire attack entrance are unable to be controlled (broken glass, etc.).

Tactical situation requires frequent entry/exit, which will prevent this tactic from working.

Fire attack entrance on the leeward side of a structure with a wind driven fire.

At least 1 firefighter must be dedicated to maintaining door control at all times. Or saw (rip) an 18” section off the bottom of the door for hose advancement.

Ideally, one firefighter at the door will maintain door position, and a second firefighter will hump hose to the door.

Firefighter on door control must be alert for signs the interior crew is evacuating.

Entry/exit into structure must be minimized until fire is under control, which can delay additional assignments (search, overhaul, and back-up).

This tactic only delays O2 introduced by the fire attack entrance. O2 introduced from any other part of the structure (i.e., a window failing) can cause rapid fire progression and endanger interior crews.




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149

Positive Pressure Attack (PPA) 150

Positive Pressure Attack (PPA) is similar to PPV, with the key difference that the PPA occurs 151

BEFORE fire attack crews make entry. 152

When all indications are present, PPA can dramatically improve visibility and reduce heat as 153

firefighters advance the attack line, allowing them to place the fire under control and search for 154

victims much more rapidly. However, if even a single indication is absent, or one of the 155

contraindications is present, PPA is extremely dangerous. Introducing large amounts of fresh 156

air to a fire with uncontrolled flow paths will accelerate its growth and cause conditions to 157

worsen rapidly. 158

In addition, the benefits of PPA are negated if it will significantly delay getting water on the fire. 159

Therefore, if PPA is to be used effectively, the initial company officer must quickly identify the 160

fire as a candidate for this tactic, and be able to establish the inlet and exhaust openings with 161

the first arriving companies. 162

If PPA is attempted, be alert for changing conditions that indicate the tactic ineffective, or 163

actively endangering firefighters. Examples include increased smoke from areas/openings 164

other than the designated exhaust opening, or no change to smoke from designated exhaust 165

opening. Both of these observations indicate that the air/pressure from the fan is not following 166

the intended flow path. PPA efforts should be immediately ceased in such cases, and not 167

resumed unless the cause can be identified and immediately fixed. 168

169


Fire under control/knocked down

Vertical/horizontal ventilation openings established, and adequate for the volume of smoke to be removed.

Use when specific exhaust opening(s) are preferred, to steer smoke away from bystanders and other hazards.

PPV is often indicated in large structures with numerous compartments, and other special situations, which are addressed in more detail in Section 4.

Unknown extent and location of fire

Exhaust opening not established.

Turning fan into building before being ordered by IC or interior crews.

Presence of explosive gasses above the UEL (upper explosive limit).

Exhaust opening on windward side of building, during high wind conditions.

Use caution in structures with large void spaces that may be concealing fire (balloon frame, common attic, etc.)

Consider using this tactic to remove the heavy smoke after knockdown of a fire when door control/anti-ventilation have been used.

Use of gas-powered fans will introduce a small amount of CO into a structure from their exhaust. This is negligible in the case of heavy smoke, but when attempting to remove a light haze, electric fans are preferred.




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*Applies to fires in small/medium size structures. Large/multistory non-combustible buildings are addressed in Section 4. 170

171

Hydraulic Ventilation 172

Hydraulic ventilation uses the air flow entrained by an interior hose stream directed out of a 173

window or exterior doorway. This tactic should not be used before knockdown, as it would 174

draw smoke and fire toward the interior crew operating the hand line. It can be used in 175

combination with other post-knockdown tactics such as PPV. 176

177

178

179

180


Fire in a known location

An exhaust opening larger

than the inlet opening (at

least 2-3 times the size of

the inlet).

Exhaust opening is in same compartment as fire.

Air can freely move from fan location → fire → exhaust opening

At least one firefighter can be assigned to stand by the fan and adjust/shut down as needed.

Fire location/compartment unknown

Exhaust opening cannot be established in the fire room

Exhaust opening smaller than inlet

Structure with vaulted ceilings or large open floor plan

Exhaust opening on windward side of structure

Firefighters or victims in windows or doorways (includes VEIS operations)

Significant openings in structure other than intended inlet & exhaust openings

Fire in void spaces of structure

Firefighters working interior prior to placement of fan

Backdraft conditions, or abnormal contents such as flammable gasses

Exhaust opening must be created prior to turning in fan*

Interior crews must be withdrawn (or confirmed to be in safe interior location) prior to beginning this tactic.

Minimize delay between turning in fan and applying water to seat of fire.

Both the inlet and exhaust opening must be constantly monitored for changing conditions.

A firefighter must be assigned to stand by the fan to shut down immediately, if needed.

Protect exposures near the exhaust opening

Buildings larger than 5000 sq. ft. will require more than one fan.

Hose streams should not be operated into an exhaust opening. Don’t try to combine PPA with a transitional attack.




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181

TACTICAL CONSIDERATIONS 182

High-Rise Buildings 183

Ventilating high-rise fires presents many challenges. Flow path considerations become more 184

important, as does use of building layout. Most high rises are noncombustible or limited 185

combustible, so the danger of collapse is decreased, but the difficulty in accessing the fire is 186

increased. Ventilation of fires in these structures will usually not be performed by the first 187

arriving company, but instead be assigned to another company or a Ventilation Group. This 188

makes coordination the key to safe and successful ventilation. 189

High-Rise: Vented vs. Not Vented 190

If a high-rise fire has not vented, the IC (or designee) should determine where the ventilation 191

opening will be, and coordinate with the attack crews as to when to create it. This may be 192

accomplished by breaking glass from an adjoining balcony, or striking it from above with a 193

hand tool suspended from a rope. The company or Ventilation Group should not create any 194

openings until requested by the attack crew, and monitor the condition of windows in the fire 195

area for signs of failure. 196

If a high-rise fire has vented, the IC (or designee) must determine the flow through the 197

ventilation opening. 198

High Rise: Wind Effects 199

Because of the increased danger posed by wind driven fires in a high-rise fire, the IC (or 200

designee) should constantly monitor all inlets/exhaust openings to the fire area for signs of 201

unidirectional inward flow or other wind driven fire behavior. Interior crews must also be aware 202

of the danger and be prepared to take refuge in internal compartments on the same face of the 203

building as the fire area. 204

205


Fire under control

Presence of firefighters interior with charged hand line

Small area requiring ventilation.

Fire not under control

Freezing conditions

Have clear visual of area that will be sprayed by hose stream. Avoid people, energized electrical lines, etc.

Position nozzle about 2 feet from window.

Avoid blocking air flow to window with your body.

Water spray should be directed to the exterior to limit property damage.




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High-Rise: Post-Fire Smoke Removal 206

Some high rises are equipped with HVAC systems that can aid in removing and replacing the 207

air inside the structure much faster than normal PPV methods. Their use should only be 208

considered if building maintenance personnel are on scene and the fire is definitively under 209

control. The IC must be informed before activating such systems. 210

Commercial Buildings 211

Large assembly, retail, and manufacturing buildings may have less windows and exterior doors 212

than a residential occupancy or high rise, which can make establishing an exhaust opening 213

adequate for the volume of fire present difficult. 214

Such buildings lack a standard layout, making universal guidelines difficult to define. In 215

general terms, attempt to establish the fire’s location, and locate the nearest existing or 216

potential ventilation openings. Ventilation efforts must be in line with the overall strategy, and 217

take advantage of building features that may allow them to create a ventilation opening, or 218

isolate the fire to a specific area within the building. Fires in these buildings may go defensive 219

if not extinguished early in the event, and a defensive fire eventually self ventilates. 220

Basement Fires 221

Basement fires are as difficult to ventilate as they are to extinguish. Ideally, they can be 222

ventilated and attacked from the same level, such as in a walk-out or daylight basement. If at 223

all possible, ventilation (and fire attack) should take place from the exterior, as opposed to 224

having crews operating above an active fire. This may involve breaching an exterior wall. 225

Another option, may be to delay active ventilation until the fire can be knocked down (or at 226

least “reset”) by exterior water application. 227

Basements that are completely below grade on all sides. In such cases, the only way to 228

effectively ventilate the structure will be through the basement stairwell. Before opening the 229

stairwell, ensure there is a single clear and unobstructed flow path for the smoke to travel to 230

the outside of the structure before opening the doorway to the basement stairs. Once the 231

basement stairs are opened, assuming this is the only opening into the basement, bi-232

directional flow should create a small layer of cool air traveling down the stairs which can be 233

used by attack crews making an advance down the stairs. 234

Another option on basement fires is to use limited ventilation tactics. This means avoiding 235

making large openings that will provide the fire with oxygen and allow it to grow, and applying 236

water to the fire area through a small hole to apply water. This could be through the floor 237

above the fire, or an exterior wall. Water can be applied by a spear nozzle, cellar nozzle, or 238

fog nozzle. The disadvantage is that any victims in the fire area will be exposed to large 239

amounts of steam for an extended period. Therefore, this tactic should only be used when no 240

survivable spaces are believed to exist in the fire area. 241

Strip Mall Fires 242

Strip malls may have a much higher fire load than a residential house, depending on the 243

business occupancy. The occupancies usually have existing openings limited to the narrowest 244




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two sides, the storefront and the rear. There typically a common attic space which can allow 245

smoke and heat to spread to exposures. Their roof construction is heavier and more time 246

consuming to cut through. 247

Ventilation tactics must be coordinated with fire attack. An early ventilation survey of the 248

structure must be performed. Note the location of any possible ventilation openings and fire 249

breaks. If crews will be making an interior attack, the flow from the nozzle will generate 250

pressure like a positive pressure fan (although less pressure in total) so if an exhaust opening 251

can be created on the opposite side of the structure, smoke and heat will tend to flow away 252

from the fire attack team. 253

Such openings may require more manpower and equipment than in a residential structure. 254

Early allocation of sufficient resources is needed to ensure the opening can be created in 255

conjunction with fire attack. Establishing a Ventilation Group will allow the IC to coordinate the 256

overall incident efficiently. 257

Some fire service texts teach setting PPV fans into exposures on either side of the fire 258

occupancy, with the idea that they will pressurize the exposures and prevent smoke/fire from 259

extending into them. However, fires generate far more pressure than a fan, and many strip 260

malls have common attics. Therefore, such a tactic is unlikely to prevent fire extension and 261

may even contribute to fire spread by introducing additional oxygen. 262

Balloon Frame Buildings 263

Balloon frame houses are common in older areas of Lawrence. Lacking fire stops between 264

floors, fire can spread much easier than in newer buildings. For these reasons, use of a 265

blower fan for PPA or PPV is contraindicated unless the fire is definitively extinguished, and 266

even then should be used with caution. 267

Limited ventilation tactics such as door control may be most useful, as they will deny a fire the 268

oxygen with which to grow in void spaces until the main body of the fire is extinguished. 269

Opening exterior walls from the outside instead of the inside can be effective and exhausting 270

smoke and heat to the atmosphere instead of allowing it to travel to different areas within the 271

structure. However, this must not be done one the windward side of the structure as such 272

openings would allow wind to introduce far more oxygen than a fan would provide, and cause 273

rapid fire growth. 274

If smoke and heat are accumulating in the attic, an exhaust opening must be created quickly to 275

prevent having fires in two locations. This could be through vertical or horizontal ventilation, 276

but should be one of the first ventilation considerations in fires that have grown past the 277

incipient stage. 278

APPENDIX / KEY CONCEPTS 279

Ventilation-Limited Fires 280

A vent limited fires growth is determined by the amount of available oxygen. Every opening 281

into a structure is a ventilation opening, whether it’s a broken window, a hole in the roof, or the 282

fire attack door. In all cases, these openings will ultimately allow more oxygen to reach the 283




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fire, which in turn will increase the size and extent of the fire. With a few exceptions, the 284

growth of the fire will be in the direction of opening. 285

Therefore, all ventilation efforts must be coordinated with the fire attack. The method, location, 286

and timing of these efforts must be purposeful and deliberate. Ventilation that occurs too early 287

or in the wrong place can increase the fire and endanger firefighters. 288

Controlled vs. Uncontrolled Ventilation Openings 289

Controlled ventilation openings are created by using existing openings in the buildings (e.g. 290

opening doors, hatches, windows, etc.), and can be re-closed if needed. Uncontrolled 291

ventilation openings are permanent openings, typically created by cutting or breaking some 292

part of the structure, and cannot be re-closed during the incident. 293

Controlled openings are preferred if available. For instance, if it will not otherwise delay 294

operations, forcing a lock on a tempered glass door is better than breaking the glass, because 295

if the door remains intact the opening can later be closed if ventilation needs change. 296

However, many buildings do not offer controllable openings in the quantities and locations 297

needed to provide adequate ventilation and uncontrolled openings must be created. 298

The Attack Door IS Ventilation 299

Interior fire attack will almost always involve opening an exterior door and advancing a hose 300

line through it to the seat of a fire. One of the key findings from modern fire science research 301

is that when this door is opened it serves as a significant ventilation opening, which was often 302

overlooked in years past. This means that the high-pressure smoke and heat flow toward that 303

opening, drawing the fire toward the attack crew. It also allows fresh air, with additional 304

oxygen to be drawn toward the fire at the floor level, intensifying the fire. 305

Research suggests that from the time the front door is opened crews have only a few minutes 306

to advance to the seat of the fire before the additional oxygen creates a rapid growth of fire. A 307

rule of thumb is that this will happen within 100 seconds in a 1-story house, and within 200 308

seconds in a 2-story house. Forcible entry efforts should attempt to preserve the door intact, 309

and a door should not be left open until the attack crew is making entry. 310

Flow Paths 311

A fire produces hot air and gasses as a product of combustion. These are at a higher 312

pressure than the rest of the environment. In a structure, this causes air pressure to build up 313

in the fire compartment. Since gas pressures always try to equalize, the atmosphere in the fire 314

compartment will flow into adjacent lower-pressure areas. This is how the fire spreads 315

pressure, heat, and smoke throughout the structure. 316

At the same time, as the fire consumes the oxygen present in the fresh air around it, it will 317

create a localized LOW pressure around its base. This low pressure will draw in fresh air from 318

any areas that have a higher pressure to the seat of the fire. 319

The fire’s flow path refers to the route taken by fresh air to the seat of the fire, and by the heat 320

and smoke travelling away from the seat of the fire. The flow path can change as the 321

exhaust/inlet openings change, and in response to firefighting tactics. 322




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Understanding the effect of flow paths on a fire, and of firefighting tactics on flow paths is 323

essential to safe and efficient firefighting. Monitoring the changes in a fire’s flow path allows 324

firefighters to determine if ventilation and fire attack tactics are working. 325

Unidirectional Flow Path 326

A unidirectional flow path occurs when the air flow in a given pathway to/from a fire is all going 327

the same way. A simple example of this would be a building that has a ventilation opening on 328

its roof, so that the fire draws fresh air in through the ground level door, and exhausts smoke 329

and heat through the hole in the roof. 330

Bi-Directional Flow Path 331

A bi-directional flow path is one in which fresh 332

air is drawn in to the fire on the floor level, 333

while superheated smoke and gas are pushed 334

away from the fire at the upper level of the 335

same path. A simple example of this would be 336

a fire in a room with a single opening. Most 337

doorways firefighters enter for interior attack 338

will have bidirectional flow. 339

The Neutral Plane 340

The neutral plane is the level in an 341

opening with bidirectional flow where the 342

exhaust flow and the inlet flow meet. This 343

level will change in response to fire 344

growth and firefighting tactics. Monitoring 345

the behavior of neutral planes throughout 346

a structure helps gauge the 347

effectiveness of these tactics. 348

The neutral plane of ventilation 349

openings can change for a number 350

of reasons. Therefore, it is 351

important to confirm that any 352

observed changes match expected 353

behavior. If they do not, it may be 354

an early warning sign of additional 355

unrecognized incident factors and 356

dangers. 357

If the neutral plane is descending, 358

as seen in Figure 5, the opening 359

is serving as an exhaust for more 360

products of combustion. This might 361

be due the fire growing in response 362

Figure 3: Unidirectional flow path

Figure 5: Neutral plane in doorway

Figure 4: Bi-Directional flow path




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to getting additional oxygen or fuel. However, the neutral plane could also descend in 363

response to changes in other openings affecting the ventilation profile. For instance, if an 364

open door that was serving as an exhaust outlet for half of the heat and smoke is closed, then 365

the other openings may see their neutral planes descend. 366

Any opening through which crews are operating interior should be monitored for signs that the 367

neutral plane is descending. This may be a sign that the fire is intensifying and expanding in 368

the direction of interior firefighters. 369

If the neutral plane is rising, it is typically a sign that the opening is being used more to draw in 370

fresh air and acting less as an exhaust outlet. This may be a good sign, suggesting the fire 371

growth is being checked by attack efforts. However, it may also be a sign of caution, 372

suggesting the fire is growing rapidly in another direction. This is especially true when the 373

opening under consideration is on a lower story than other openings. 374

Dangers of Operating in an Exhaust Flow Path 375

The exhaust flow path is the route taken by the hot air and smoke to the outside of the 376

structure. 377

Almost all interior fire attacks will require firefighters to operate in a flow path at some point. 378

This is not a contraindication, but firefighters must be aware that operating in an exhaust flow 379

path can cause PPE to fail earlier than expected. Just as wind makes cold air feel colder, 380

rapid movement of hot air past a firefighter transfers much more heat energy than relatively still 381

air of the same temperature. 382

There are several solutions to this issue which may be possible, depending on tactical 383

considerations. They include: 384

Opening hand lines into the flow path. This protects crews and also creates an interior 385

pressure back toward the fire as the hose stream entrains air in the direction of the water flow. 386

This may also check the growth of the fire until the line can be advanced to the seat for knock-387

down. 388

Withdrawing crews to change tactics or repositioning them to enter via a different attack 389

opening. This is especially true for firefighters operating interior above the fire level. 390

Isolating crews from the flow path – in a high rise or other building with long hallways, crews 391

may avoid the exhaust flow path by sheltering in place in a nearby compartment that can be 392

isolated from the flow path and the exterior. 393

Opening additional exhaust vents – this should be done in a coordinated manner, as described 394

in this SOP. 395

Partially or totally closing the exhaust vent – if the exhaust vent is the attack entrance, it cannot 396

be completely sealed due to the hose line in the doorway. However, it can be significantly 397

sealed by limited ventilation tactics (described above) such as door control or smoke curtains. 398

This will not cool the temperatures in which the crews are operating, but it will decrease the 399

rate at which the superheated air flows past their protective gear, and thereby prolong its 400

efficacy. 401

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Lawrence-Douglas County Fire Medical 207.42 Procedure and Procedures/SOPS/SOP PDF...Lawrence-Douglas County Fire Medical Procedure 207.42 Title: Ventilation Effective Date: Draft Page