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What are the two primary types of dangerous building conditions during a fire?

Conditions that contribute to fire spread/intensity and conditions that make the building susceptible to collapse.

How are fire spread and structural collapse related?

Conditions that increase fire spread and intensity can also increase the likelihood of structural collapse.

What does a building's construction type rating indicate?

How long the construction type is expected to maintain structural integrity under specified conditions.

What factors can make a building's actual fire resistance different from its estimated resistance?

Fire duration before arrival, building contents, heat release rate, fire intensity, and renovations that may compromise fire resistance.

What is fuel load?

The total quantity of combustible contents in a building, space, or fire area.

What materials can contribute to a building's fuel load?

Wood framing, floors, ceilings, furnishings, and other combustible materials.

How does a high fuel load affect fire development?

It provides more fuel for pyrolysis and combustion and can increase fire intensity, heat release rate, and fire spread.

Why are synthetic furnishings particularly important to fire dynamics?

They can pyrolyze rapidly and produce high heat release rates.

How does fuel orientation and surface-to-mass ratio affect fire spread?

Higher surface-to-mass ratios and favorable fuel orientation can increase the rate and intensity of fire spread.

How does fire location within a building affect fire development?

Upper-level fires generally spread downward more slowly, while lower-level fires can spread vertically through heat currents in stairways, atriums, shafts, and concealed spaces.

Why are concealed spaces dangerous?

Fire can spread through hidden cavities, making it harder to locate and extinguish and increasing collapse risk.

Why are preincident surveys important in large commercial, industrial, and storage buildings?

They provide information about hazards and help firefighters understand the building before an emergency.

How can a high fuel load affect a ventilation-limited fire?

It can leave large amounts of unburned fuel gases that may reignite when oxygen is introduced.

What are examples of combustible interior finishes?

Drapes, wallpaper, and carpet.

What are examples of furnishings that contribute to fuel load?

Tables, sofas, desks, and beds.

How can combustible exterior wall coverings affect fire spread?

They can add wood or petroleum-based fuels to the building and spread fire to other areas or adjacent exposures.

Why are combustible roofs a community fire hazard?

Flaming embers can ignite combustible roof coverings and spread fire from building to building.

Why are wood shakes dangerous during wildland/urban interface fires?

They can significantly contribute to fire spread even when treated with fire retardant.

What can happen when combustible materials are installed over a metal roof deck?

Fire below the deck can melt or ignite combustible insulation or roofing layers and cause fire above the roof.

How does building compartmentation affect fire behavior?

It affects fire development, severity, duration, and intensity.

What building layout features affect fire development?

Number of stories, floor plan, openings between floors, continuous voids/concealed spaces, and barriers to fire spread.

How can compartmentation help firefighters?

Fire-rated walls, ceilings, and doors can separate fuel sources and limit fire development to individual compartments.

When are two rooms considered separate compartments?

When the doorway between them is closed.

How can firefighters use doors during interior operations?

Doors can be closed when appropriate to control oxygen sources and flow paths.

What is a major difference between modern and older residential construction?

Older structures generally had smaller, more numerous compartments, while modern homes often have open floor plans and lightweight construction.

What features may be found in modern single-family homes?

Open floor plans, high ceilings, atriums, lightweight manufactured structural components, sealed windows, wall cavities, and synthetic insulation.

How have synthetic construction materials affected fire behavior?

They increase fuel loads and can produce large quantities of toxic and combustible gases.

Why can energy-efficient buildings create difficult fire conditions?

They can contain fires longer and create fuel-rich, ventilation-limited environments.

Why are open-plan commercial buildings challenging?

They can have high fuel loads and few physical barriers to prevent fire and smoke spread.

Why are plastics and synthetic materials important in fire behavior?

They can cause fires to escalate rapidly, reach high temperatures, and consume available oxygen quickly.

What building characteristics should firefighters consider during size-up?

Occupancy, construction type, square footage, compartmentation, ceiling height, number of stories, exterior openings, stairs, shafts, roof openings, exposures, adjoining structures, roof design, fire protection systems, contents, and HVAC systems.

How does compartment size affect fire development?

Large compartments generally develop fires more slowly because they contain more air and increase the distance radiant heat must travel to reach additional fuel.

Why can high ceilings be dangerous?

Hot gases can accumulate at ceiling level while conditions at floor level remain relatively unchanged, causing firefighters to underestimate fire development.

What types of buildings can contain large open spaces?

Warehouses, churches, large atriums, large mercantile buildings, and theaters.

How can insulation affect fire development?

It can retain heat within the building, increase localized temperatures, accelerate fire growth, and sometimes provide additional fuel.

What is heat reflectivity in a building?

The ability of surfaces to reflect radiant heat toward adjacent fuel sources, increasing fire spread.

What is heat retention?

The ability of a material to absorb and slowly release heat, maintaining elevated temperatures.

How quickly can unprotected engineered steel and wooden trusses fail when exposed to fire?

They can fail after approximately 5 to 10 minutes of exposure.

Can lightweight trusses fail without direct flame contact?

Yes. They can fail from heat exposure alone.

At what temperature does steel begin to weaken according to the outline?

Approximately 1,000°F (538°C).

Why are metal gusset plates in wooden trusses dangerous?

They can fail quickly when exposed to heat.

How does traditional solid wood-joist construction typically react to fire?

It tends to lose strength gradually and may make a roof soft or spongy before failure.

Why is a soft or sagging roof dangerous?

It is an indication of structural failure, although it is not the only possible sign of imminent collapse.

Why can modern engineered joists be especially dangerous?

They can burn and fail quickly, sometimes before obvious signs appear in the roof decking.

What can happen when lightweight trusses fail?

Entire sections of decking can fall into the fire without obvious exterior indications of failure.

What is a bowstring truss?

A truss roof system commonly recognized by its arched or curved outline and historically used for large commercial or industrial structures.

Where were bowstring trusses commonly used?

Automobile dealerships and repair facilities, bowling alleys, grocery stores, and industrial complexes.

Why are older bowstring trusses especially concerning?

Trusses built before the late 1960s may have code deficiencies, including inadequate tensile strength in bottom chord members.

Why are preincident surveys useful for bowstring truss buildings?

They can reveal hidden construction features that may not be obvious during an emergency.

What happens to fire risk when a building is under construction, renovation, or awaiting demolition?

The risk of fire rises sharply.

What factors increase fire risk during construction or renovation?

Additional fuel loads and ignition sources such as cutting torches, grinding, and welding.

Why do partially completed buildings spread fire rapidly?

Protective features such as gypsum wallboard and automatic suppression systems may not yet be installed.

Why are exposed wooden frames in unfinished buildings dangerous?

They can behave like a vertical lumberyard and provide large amounts of combustible fuel.

What conditions can make abandoned or renovated buildings especially dangerous?

Breached walls, open stairwells, missing doors, deactivated suppression systems, altered components, deterioration, and increased collapse potential.

Why can renovation work make firefighter entry more difficult?

Debris and construction materials can block exits and impede both occupants and firefighters.