Firefighter Safety and Modern Building Construction

Firefighter Safety and Modern Construction

Residential fires are, by far the most common scenarios in which firefighters are killed. Take a moment and think about the building you live in. Are there hazards to firefighters  in your own home?  In this section we will discuss the features and hazards associated with modern construction materials and building contents that present a challenge to firefighters.

Frank Brannigan said it best:

“Many investigations into firefighter deaths and injuries suggest that fire departments, incident commanders, incident safety officers and firefighters may not fully consider information related to building occupancy before performing offensive operations or entering structures to initiate interior operations.”

“There is no safe time under or on burning trusses. You can have a raging fire over your head or under your feet and not even know it. There is no obligation to kill firefighters to save a disposable building. Paste this on your helmet.”  -Frank Brannigan (Fighting Fires in Unoccupied Structures, NIOSH)

INTRODUCTION

Building construction and furnishings have changed dramatically over the last three decades, but the tactics and equipment used by firefighters has changed very little. These new methods of construction and new materials used in the manufacture of building contents negatively impact firefighter safety. This is not an unknown problem. Many studies point to concern involving modern construction. Changes in fire behavior that require a renewed focus on how to properly handle these incidents is now a reality. While we haven’t necessarily changed what the fire service does or how they do it, we can change our behavior by examining the effect new building construction materials and techniques and furnishings have had on the burning characteristics of today’s structures. Becoming aware of how those new burning characteristics impact firefighter safety is a critical skill set.

This problem is not just about lightweight construction. Fires create highly toxic environments. We have a greater fuel load, and faster fire propagation.

This section is designed to provide the reader with some information about the modern fire environment and act as a reminder of some things to enhance their safety when fighting a fire involving modern construction. The intent is to make sure that the reader is aware of the potential risks and hazards firefighters face when responding to an incident.

A hazard is defined by the NFPA as a condition, an object, or an activity with the potential of causing personal injury, equipment damage, loss of material, or reduction of the ability to accomplish the mission.

A risk is defined by the NFPA as the chance of injury or loss.

Firefighters are at Risk!

Firefighters are at increased risk of death and injury due to trauma while working inside of common residential occupancies. Extreme fire behavior and the failure of the building from collapse is frequently a causal or contributing factor in traumatic fatalities during structural firefighting operations.

Definition of Residential Building

A structure is a constructed item of which a building is one type. The term residential structure commonly refers to buildings where people live. To coincide with this concept, the definition of a residential structure fire includes only those fires confined to an enclosed building or fixed portable or mobile structure with a residential property use. Such fires are referred to as residential buildings to distinguish these buildings from other structures on residential properties that may include fences, sheds, and other uninhabitable structures. Residential buildings include, but are not limited to one- or two-family dwellings, multifamily dwellings, manufactured housing, boarding houses or residential hotels, commercial hotels, college dormitories, and sorority/fraternity houses.

Part of the concern with modern construction stems from the perception that the structural fire resistance of “conventional” woodframe construction provides a much greater degree of safe working time than for modern construction. As a practical matter, no two fires are the same and a structure’s fire endurance and mode of failure under real fire conditions is unpredictable. Time can quickly be forgotten on the fire-ground and firefighters may not be able to determine if the safe working time has already been exceeded when they arrive.

This necessitates a rethinking of tactical procedures and guidelines for fighting fires in these newer structures or newer contents. Using the same tactical thinking, procedures, and timelines that were commonly used in years past are not the best applicable for modern construction or modern contents. For more specific information please see the UL /NIST videos showing time to flashover in a compartment fire. (http://www.nist.gov/fire/)

“If you are not acquainted with the structure of the fire building, whatever its age, assume that it contains lightweight materials and construction methods. Today, building officials nationwide are approving remodeling plans for buildings of sawn lumber construction, using wood trusses and I-joists. I have seen these components used in remodels of century-old mill (Type IV) and Ordinary (Type III) buildings as well as Type V wood frame. This is especially true when these old factory and mercantile buildings are turned into apartment buildings and condominiums.”  -Gregory Havel

Model of Modern Firefighting Tactics and Strategies

Model of Modern Firefighting Strategy and Tactics

 

Description of Model

This model compares the passage of time with the stability of a structure. On the lower left of this model indicates a building that does not contain a fire and has a high degree of structural stability. The right side of the model discusses what happens if the building is totally involved in fire and the structure is unsafe. To understand this model, you need to follow three factors; what happens to the building when it is on fire and what happens to the stability of that building as the fire progresses. That is reflected by the line that goes from the lower left to upper right. The second thing for consideration is the time of arrival of firefighting personnel. It can either be before the building is badly involved and remains fairly stable or it can occur after the building has been assaulted by fire and is beginning to become unstable. The third factor is the decision point to either engage in offensive tactics or defensive tactics.

The dotted line on the model is a variable. In essence you can arrive at a building on fire very early on or you may arrive late in the fire’s development. As a responder, you are unlikely to know how long the fire has been burning until you get a chance to assess fire conditions. The problem occurs when the building has been burning for a considerable period of time and does not show any visible evidence of structural integrity degradation. This would include evidence from both both smoke and heat (flame). This line is also affected by the nature of the contents of the building. Heavy smoke conditions can often obscure the amount of fire damage that has occurred. Smoke potentially contains large amounts of unburned fuel. Ventilation by the firefighter can accelerate fire growth. Caution should be exercised when ventilating structural fires. For purposes of establishing a criterion for success, the fire department needs to make decisions about being offensive or defensive before structural conditions become unstable. Scientific Information Contemporary literature on modern firefighting emphasizes that the order of execution for tactics and strategy may vary depending upon how much you can control the air and/or the heat. The order of that execution may actually vary from Layman’s concept of RECEO. The new sequence of events might well be the following:

  • Decision to enter
  • Cover and confine
  • Ventilation
  • Search
  • Extinguishment

Before talking about modern tactics, we should review the most fundamental tactics and strategy document created for the fire service. This document is Firefighting Tactics, Lloyd Layman, NFPA. Basic Divisions of Firefighting Tactics Size Up or Estimate of the Situation (This now also includes the term “situational awareness”) In the past this was defined as the mental evaluation made by the operational officer in charge of a fire or other emergency. This process enabled the incident commander to determine a course of action and to accomplish the mission. One of the most significant changes in the concept of size-up is the idea that firefighter safety is now the number one priority for the incident commander. (16 Life Safety Initiative, National Fallen Firefighter Foundation)

1. Firefighter Safety – Includes those decisions which are required to prevent firefighters from being unintentionally exposed to conditions that could result in severe injury or death. It is a determining factor as to whether actions will be offensive or defensive.

2. Rescue – Includes those operations which are required to remove human beings from an involved building or other hazardous situation and convey them to a place of safety.

3. Exposures – Includes those operations which are required to prevent a fire from extending to uninvolved buildings or separate units.

4. Confinement – Includes those operations which are required to prevent a fire from extending to uninvolved sections of a building.

5. Extinguishment – Includes those operations which are required in attacking and extinguishing the main body of fire. Modern building construction and building content must be considered to determine whether the fire is fuel driven or ventilation driven.

6. Overhaul – Includes those operations which are required to complete the extinguishment of remaining fire, prevent rekindling and to place the building in a safe condition.

A. Ventilation – Includes those operations which are required to displace a heated and confined atmosphere within an involved building with normal air from the outside atmosphere. In modern construction, this also involves consideration of the actions taken by firefighters that can have an effect upon the actual flow path of a fire. It is now recognized that actions taken by firefighters can have an adverse impact upon fire spread.

B. Salvage – Includes those operations which are required to protect buildings and contents from preventable damage due to water or other elements. Modern building construction and content now recognizes that once a fire is extinguished that an atmosphere that is immediately dangerous to life and health (IDLH) can exist in the salvage phase and that self-contained breathing apparatus should be utilized unless conditions have been measured and found safe.

In summary, Layman laid out the operational considerations that would have to be addressed but did not go much further into the “how to do these things”. The word safety was not included anywhere in the narrative of the text. Layman’s use of the concept of size up seemed to be focused more on the incident commander rather than the firefighter. This makes it easy to feel that Layman’s construct may not be up to speed with contemporary decision making factors.

Contemporary Texts

Safe and effective fire-ground operations require knowledge of fire dynamics and building construction. The creation of the concept of situational awareness by Richard Gassaway, and others provides a transition between Layman and all other future considerations. This next section addresses how contemporary recommendations have expanded upon Layman’s framework. ( Gassaway, Richard, Situational Awareness.) (Ten Rules for Survival )

Fire Behavior (important because of changing contents)

This requires a solid understanding of the key fire behaviors and the relationship between these behaviors and the actions being taken by the fire fighters themselves. Tactics used by the firefighters can influence the fire’s development and direction of travel.

  • Fuel Driven Fires – this requires a basic understanding of fire behavior.
    • Time Elements of Fire Behavior
    •  Products of Combustion of Modern Fuels
    • Stages of Fire Development
  • Ventilation Driven Fires – this requires an understanding of flow path.
    • Flow Path – “every new ventilation opening provides a flow path to the fire and vice versa. This could create a very dangerous condition when there is a ventilation limited fire.” (Kerber, Steve, Underwriters Laboratory) This requires that firefighters be aware of flow path and air track. Flow path is the course of movement that hot gases follow between the fire area and exhaust openings. It affects the movement of air into the fire. Air track is considered closely related. Air track is the observation of the movement of both air and smoke as observed from the perspective of inside or outside of the structure. Air track terminology describes a group of fire behavior indicators. These indicators include direction and intensity of smoke, velocity and turbulence and movement between the upper and lower boundaries of thermal balance. (http://cfbt-us.com/wordpress/?tag=situational-awareness)
      • Contaminated Atmosphere – the products of combustion of modern fires have clearly been a source of injury and fatality of firefighters. The term used to describe this contamination is called Immediately Dangerous to Life and Health, (IDLH). For specific information on how to protect yourself from IDLH, review websites listed in the website contacts at the end of this document.

Building Construction (Important because of components)

  • Fire Resistance Issues
  • Legacy vs Contemporary Lumber

Structural Collapse (Fire and life safety issue)

  • Load Path
  • Fighting Fire in Structures

This has resulted in a new Time Frame for decision making. The following is a modern versus legacy timelines.9

modern timeline rev

This research examines a consistent change in the residential fire environment. Firefighters must change their approach to these fires or suffer the consequences. For further information see Kerber, Steve, Analysis of Changing Residential Fire Dynamics and its Implications on Firefighter Operational Timelines, UL.

time to flashover

Fire Service arrival times versus Fire development

This chart clearly illustrates the shortening of the time frames for safe operations by the fire service and should be considered in all tactical decision making. Do you have the time to do what you want to do to control the situation? The following chart gives you some estimate of the times that have been derived from tests conducted under scientific control.

unprotected structural element testing

Importance of Pre-Fire Planning

Pre-fire planning is defined as the study of buildings to prepare for an eventual fire. The changes in modern building construction and the content have significantly increased the importance of pre-fire planning. Those departments that do not engage in pre-fire planning are gambling on the safety of their personnel. For local application, see NFPA Standard on Pre-Fire Planning. (See NFPA Standard 1620- Pre-Incident Planning, Current Edition, Quincy MASS)

Go into the field and inventory buildings in your area that might create hazards when the buildings involved in fire.

Fire Resistance Issues

  • All buildings are built with some consideration of fire resistance. That is the nature of such things as fire walls and area limitation. However, once a fire occurs in a building the manner in which it progresses may or may not be in accordance with the original code provisions. There is no such thing as a fire proof building. Even buildings constructed entirely with non-combustible material can suffer major damage due to a fire contained to the contents of that building. Fire resistance performance should include all of the following:
    • Structural components, exterior and interior finish components, building contents, detection and alarm systems, exit design, built-in fire protection systems, property setbacks from adjacent buildings or exposure to other fire hazards, ease of access for firefighters and the availability for firefighting services.

Structural Collapse (Fire and Life Safety Issue)

The combination of all hazards associated with buildings can create an environment in which firefighters lives can be lost. The issue of an unlikely and unpredictable collapse should be of prime importance to the incident commander. Firefighters should use extreme caution when operating on or under either an attic or basement fire. In multistory buildings, operating above any fire is dangerous. The department should have written SOPs for emergency warning to order an evacuation. The SOPs should include but not be limited to instant accountability for crews on the scene.

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STRUCTURAL COLLAPSE?

  • Incident Command – duration of burn
  • Size-up – interior/exterior conditions and signs
  • Lightweight Construction – truss/masonry veneer walls/chimney
  • Sound out floor/surfaces upon entry
  • Be aware of area weight capacity – standing water & personnel
  • Heavy suspended mechanical equipment
  • Collapse zone – 1.75 X.

Load Path

Strengthening the structural frame of a building involves the idea of creating a “continuous load path” within your structure. So what is a continuous load path? It’s a method of construction that uses a system of wood, metal connectors, fasteners (like nails and screws) and shearwalls to connect the structural frame of the house together from top to bottom. Maintaining a continuous load path is important to preventing the building from having a structural collapse. This is not unlike the idea that a chain is not any stronger than its weakest link. A Load Path ties the house together from the roof to the foundation. When any component is damaged by fire it can fail, thereby compromising the rest of the structure.

The direction that loads are transferred through any specific structure is important and must be identified as quickly as possible when the building is on fire.

  • the footings support the flooring structure which consist of bearers, joists and flooring
  • the stud walls and bracing transfer their load to the flooring
  • the roof trusses support the battens which support the roof cladding and this load is transferred to the walls.

Although modern building codes require homes to be built with a continuous load path, older buildings may not be built to that standard. In addition not all parts of the country follow national building standards. The age of a building can also help determine whether it has a continuous load path or not. Older homes, built before 1985, typically do not have a continuous load path. Homes built after that may have a load patch, but the components may not be of the same design as the older buildings. Modern construction techniques may consist of lighter weight structural components. To help you learn more about the structural integrity of buildings and how to fight fires within them, you should be knowledgeable on structural safety.

Recommended guidelines for fighting fires in residential structures

Before you enter a building that is on fire you should consider the following:

  • Do you know how to determine the occupant Survival Profile? If the answer is no – then go to the IAFC website at http://www.iafc.org/Operations/LegacyArticleDetail.cfm?Ite mNumber=4486 and review the proposed process there.
  • Can you determine the possibility or probability that the occupants have still survived?
  • The company officer and firefighter have to be able to consider fire conditions in relation to possible occupant survival if a successful rescue event is going to be part of their initial and ongoing individual risk assessment and action-plan development. 
  • The fire service has a long history of aggressive search and rescue operations as an initial priority of first arriving fire companies. History (and firefighter fatalities) also reflects that firefighters are exposed to the greatest risk of injury and death during primary search and rescue operations. Search efforts must be based on the potential to save lives.
  • A safe and appropriate action plan can’t be accurately developed until we first determine if any occupants are trapped and can survive the fire conditions during the entire rescue event (find and then remove them).
  • If survival isn’t possible for the entire extraction period, a more cautious approach to fire operations must be taken. Fire control should be obtained before proceeding with the primary and secondary search efforts.

Firefighters must understand the dangers of any structural component exposed to direct fire, regardless of the component material, especially when there are large amounts of stored items such as furniture or other items within the area. It is important to consider that all building components must be designed, installed and maintained properly in order to perform properly. In many cases, homeowners are asking for much larger spans without intermediary support of the structural components.

Although the 2012 Edition of the International Residential Code required protection on the basement ceiling side of a structure, most residential buildings built before this code will not have this protection. Over the years, there have been collapses involving basement fires that have led to firefighter entrapment. They have involved many different types of construction. On all incidents it is necessary to examine the conditions present and determine if the risk of attempting to save lives outweighs the danger of putting out the fire with an interior attack. It is recommended that tools such as a thermal imaging camera be used to examine for hidden fires or those affecting a focused area of the structural components. NIST has conducted research on these devices. This research clearly describes the limitations of the thermal imaging camera. They should not be used as the only tool during initial size up or ongoing situational awareness. It is necessary for all firefighters to review buildings during construction and become familiar with the different products installed in buildings today.

fire propogation

(Kerber, Steve, Analysis of Changing Residential Fire Dynamics and its Implications on Firefighter Operational Timelines, UL)

Study Links to Further Information Regarding Fighting Fires in Modern Building Construction

It is strongly recommended that you visit these websites and obtain your own library of information. This information can be used to enhance your decision making abilities on the fire ground.

Modernfirefighting.org

American Wood Council – http://www.awc.org/

American Iron & Steel Institute – http://www.steel.org/

Buildings on Fire – http://buildingsonfire.com/

CFBT http://cfbt-us.com

Fire Chief Magazine – firechief.com

Fire Rescue Magazine – http://www.fire-rescue.com/

Fire Engineering Magazine – http://www.fireengineering.com/

International Association of Fire Chiefs – http://www.iafc.org/ http://commandsafety.com

Structural Building Components Association http://www.sbcindustry.com/firepro.php

Woodaware.org

United States Fire Administration – http://www.usfa.fema.gov/

BIBLIOGRAPHY

NIOSH Alert Document – Preventing Injuries and Deaths of Firefighters due to Structural Collapse

NIOSH Alert Document – Preventing Deaths and Injuries due truss system failures.

UL Document – Analysis of Changing Residential Fire Dynamics, and its implications on firefighter operational time frames.

Dunn, Vincent, Collapse of Burning Buildings, A Guide to Fireground Safety, Fire Engineering. Tulsa, Oklahoma, 2010

www.idbdtraining.com

Additional information on these topics can be found at Modernfirefighting.com

Glossary

Construction: Traditional Construction: of or pertaining to a characteristic of “older” styles of a particular product or process. It is recognized that many of the changes in construction started about 1970. Generally involves dimensional lumber

Modern Construction – of, relating to, or characteristic of the present or the immediate; of, relating to, or characteristic of a period extending from a relevant recent past to the present time. In this case it means buildings built after 1970 and includes those built yesterday.

Legacy Construction – of or relating to, or characteristic of the past practices of the construction industry. This could involve buildings that are over 100 years old.

Engineered Construction -Engineered wood products can be defined as products consisting of a combination of smaller components to make a structural product, designed using engineering methods. They are an alternative to traditional sawn lumber

Fire Resistance – A fire-resistance rating typically means the duration for which a passive fire protection system can withstand a standard fire resistance test. This can be quantified simply as a measure of time, or it may entail a host of other criteria, involving other evidence of functionality or fitness for purpose.

Fire Stopping – (Fire Blocking) Building materials or approved materials installed to resist the free passage of flame to other areas of the building through concealed spaces.

Flame Spread is a rating is a ranking derived by laboratory standard test methodology of a material’s propensity to burn rapidly and spread flames. There are several standardized methods of determining flame spread,

Flow Path is the course of movement that hot gases follow between the fire area and exhaust openings. It affects the movement of air into the fire. Air track is considered closely  related. Air track is the observation of the movement of both air and smoke as observed from the perspective of inside or outside of the structure. Air track terminology describes a group of fire behavior indicators.

I-Joists – Wood I-joists are composed of two horizontal components called flanges and a vertical component called a web. Wood I-joists are used as a framing material primarily in floors, but may also be used as roof rafters where long length and high load capacity are required.

IDLH – IDLH atmospheres are capable of causing death, irreversible adverse health effects, or the impairment of an individual’s ability to escape from a dangerous atmosphere. SEE WEBSITE http://www.cdc.gov/niosh/idlh/idlhintr.html

Lightweight Construction – Lightweight construction is a method of construction using lightweight materials such as plaster, wood, glass, aluminum, steel or similar materials and in this way is different from conventional construction that uses concrete and masonry. This is a type of construction where vertical and horizontal structural elements are primarily formed by a system of repetitive wood or cold formed steel framing remembers. Engineered wood products can be defined as products consisting of a combination of smaller components to make a structural product, designed using engineering methods. They are an alternative to traditional sawn lumber.

Load Path – Strengthening the structural frame of a building involves the idea of creating a “continuous load path” within a structure. A load path is a method of construction that uses a system of wood, metal connectors, fasteners (like nails and screws) and shear-walls to connect the structural frame of the house together from top to bottom. Maintaining a continuous load path is important to preventing the building from having a structural collapse. This not unlike the idea that a chain is not any stronger than its weakest link. A Load Path ties the house together from the roof to the foundation. When any component is damaged by fire it can fail, thereby compromising the rest of the structure.

Occupant Survival Ability Profile – determining if any occupants are trapped and if they can survive the current and projected fire conditions.

Situational Awareness – The perception of environmental elements with respect to time and/or space, the comprehension of their meaning, and the projection of their status after some variable has changed, such as time, or some other variable, such as a predetermined event. In the case of the fire service Situation Awareness is related to Building Construction, Command Risk Management and Firefighter Safety is another mission critical element.

Toxicity is the degree to which a substance can damage a firefighter when exposed to IDLH.