Chapter 5 Fire Behavior and Building Construction

Objectives Identify fundamentals of fire behavior and key fire phenomena. Describe the development of a compartment fire. Identify the ways fire is influenced by a building and its characteristics.

Objectives List the ways buildings and their components are affected by a fire. Explain how specific building materials behave under fire attack. Describe smoke behavior and the effects it can have on the building, occupants, and fire fighters.

The Basics of Fire and Fire Behavior Fire requires four elements: Fuel Oxidizing agent Heat Uninhibited chemical chain reaction

The Basics of Fire and Fire Behavior Three methods of heat transfer: Conduction contact Convection Radiation Courtesy of Richard Wolfson. Courtesy of Glenn Corbett.

The Basics of Fire and Fire Behavior Autoignition: a combustible material ignites spontaneously Autoexposure: vertical spread of fire on the exterior of a multistory building

Compartment Fires Compartment: the enclosure around a fire Four stages of a fire: Incipient Free burning Flashover Smoldering/ decay Reproduced with permission from NFPA 921-2011, Guide for Fire and Explosion Investigations, Copyright © 2011, National Fire Protection Association. This reprinted material is not the complete and official position of the NFPA on the referenced subject, which is represented only by the standard in its entirety.

Compartment Fires Elements of a compartment fire: Fire plume Smoke Heated gases Ceiling layer Neutral plane

Compartment Fires Entrainment Flameover Oxygen supply Wind-driven fires must be considered tactically. Fire blanket Courtesy of NIST.

Compartment Fires Construction factors influencing fire behavior: Combustible interior finishes or walls Vertical openings Height of the fire room Proximity of walls to each other HVAC systems

Backdraft Burning of heated gaseous products when oxygen is introduced into an environment whose oxygen supply has been depleted

Fire Behavior, Fire Fighters, and Buildings Hazards in addition to collapse: Flashover Backdraft Concealed fires Rapid spread of fire Ventilation Abnormal situations warrant a thorough investigation.

Fire Growth and Spread Growth and spread are influenced by building construction. Combustible acoustical tile is fiberboard into which holes have been punched. Courtesy of the NFPA.

Examples of Fire Growth and Spread Rapid fire growth = serious losses of life Combustible ceiling tiles suspended below the floor above = void for holding CO gas Ignition of trapped CO gas = violent explosion

Building or Contents Hazard? Fire growth building problems can be hidden or exposed. Fire growth contents problems can be due to: Furnishings Interior finish/decorations Mercantile stock High flame-spread materials contribute to fire growth, smoke, and toxic products.

Hidden Building Contents Batt insulation Sprinklers may not reach a fire spreading above the ceiling. Combustible fiberboard Foamed-plastic insulation Protected with a half-inch gypsum board covering Electrical insulation

Interior Finishes Plaster Interior finishes may increase fire hazard via: Increasing fire extension Generating smoke and toxic gases Contributing to flashover Low-density fiberboard Cheap interior finish Quick installation

Interior Finishes Combustible acoustical tile Installed over the original ceiling Industry opposition to regulation of interior finishes NFPA opposition to fiberboard Courtesy of Glenn Corbett.

Other Hazards Associated with Interior Finishes Adhesives High-density fiberboard Paper © Saxon/AP Images.

Other Hazards Associated with Interior Finishes Fabrics Cork Rattan Wood © AP Images

Other Hazards Associated with Interior Finishes Plastics May be disguised as wood or glass Ireland’s Tribunal of Inquiry Architects may not recognize potential combustion problems. © Norman Pogson/ShutterStock, Inc.

Other Hazards Associated with Interior Finishes Worcester Cold Storage Warehouse Fire 1999 Carpeting © Paul Connors/AP Images.

Additional Hazards Void spaces Remodeled ceiling hazards Suspended ceilings of combustible tile form void spaces. Remodeled ceiling hazards Removal of old ceilings is not required. Courtesy of the estate of Francis L. Brannigan.

Additional Hazards Aircraft interiors Acoustical treatment Aircraft built after 1990 have to meet stricter FAA standards. Acoustical treatment Open-plan offices create a potential hazard. Corridors © bhowe/ShutterStock, Inc.

Additional Hazards Alterations Decorations and contents Major fire hazards Christmas trees Haunted houses Glass fiber-reinforced plastic

Today’s Fire Loads Fire loads and rates of heat release are greater today than when fire codes were first written. First Interstate Bank Fire Hotel remodeling Regulations California Boston Port Authority of New York and New Jersey

Today’s Fire Loads Certification of interior designers Residential fire tests Report on NBS 1980 residential fire tests NFPA movies Fire: Countdown to Disaster Fire Power

Control of Rapid Fire Growth Eliminate high flame spread surfaces Separate the material from the source of combustion Cut off the extension Coat the material Fire-retardant surface coatings Pressure-treated, fire-retardant wood

Products of Combustion Smoke Airborne solid and liquid particulates produced by a fire CO, hydrogen cyanide (HCN), and carbon dioxide More damage to property than fire or water

Products of Combustion Smoke Gases Cause injury or death when inhaled or absorbed Concentration and exposure time 1929 Cleveland Clinic Fire Polyvinyl chloride (PVC) Courtesy of the National Board of Fire Underwriters/NFPA.

Gas Flammability CO is a flammable gas. Combustion leads to flashover or backdraft. Gases accumulate in enclosed areas. Ventilation does not prevent CO explosions.

Physical Effects of Smoke Different physical effects on people CO is colorless, odorless, and tasteless. Smoke particles can preventing air filtering.

Contaminated and Toxic Smoke Smoke damage may be the most expensive by-product of a fire. Contamination with radioactive material or polychlorinated biphenyl (PCB) Cost of a cleanup Hanford, WA, nuclear power plant cleanup Toxic effect of PCBs

Corrosion and Smoke Movement Plastics containing halogens can form corrosive acids. Fire gases rise due to buoyancy.

Summary Fire behavior is critical for all fighters Compartment fires are complex and dynamic Fire behavior is influenced by building construction Fire fighters are at great risk from rapid fire growth High flame spread materials Several possible approaches to control the problem of fast fire growth

Summary Smoke used to describe the collective group of solid and liquid particulates and gases. can affect occupants, fire fighters, and buildings in many ways.