Investigación de Incendios Forestales Nivel 2, Unidad 1 "El Incendio Forestal y su comportamiento"

Introduction to Fire Investigation

Welcome and Course Overview

• The speaker welcomes participants from Mexico, Argentina, and Chile, expressing excitement for the course's commencement.

• A technical issue caused a one-week delay in starting the course; however, this was seen as beneficial for better preparation.

Speaker's Background

• The speaker has been involved in fire investigation since 2018, with experience across various organizations including factories and international police.

• They have completed extensive training in fire origin and cause investigation, accumulating 99 hours of specialized courses.

Key Topics in Fire Investigation

Training Requirements

• The training covers 16 essential topics required by ANFP for fire investigators, including dynamics of explosions and evidence collection at fire scenes.

Essential Concepts

• Important subjects include basic electricity, interview techniques, scientific methods related to fires, report writing on origins and causes of fires.

Understanding Fire Behavior

Origin of Fire

• Discussion will cover the origin of fire through concepts like the fire triangle and tetrahedron which are crucial for understanding combustion processes.

Historical Context

• The significance of fire throughout human civilization is highlighted; it has been used for cooking and energy production since ancient times.

Mythological Perspectives on Fire

Prometheus Myth

• Reference to Prometheus stealing fire from Zeus symbolizes humanity's relationship with fire; it represents both creation and punishment within mythology.

Religious Interpretations

• In various religions, fire is not merely destructive but also signifies renewal or rebirth. This duality emphasizes its importance in spiritual contexts.

Scientific Understanding of Combustion

Flogiston Theory

Understanding Combustion and Fire Dynamics

Theories of Combustion

• A chemist and biologist in the late 18th century demonstrated that combustion is a result of an exothermic chemical reaction, challenging previous theories.

• Combustion is defined as a chemical reaction between a fuel and oxygen, requiring heat to initiate. This process produces various combustion products such as smoke, gases, vapor, and solid residues.

Definition of Wildfires

• According to forest law (Law 583), fire is characterized as any uncontrolled propagation regardless of its origin or size in rural areas and urban-forest interfaces.

• The discussion will focus on how combustion originates and transforms into uncontrolled fires or wildfires.

Conditions for Combustion

• For combustion to occur, a minimum oxygen concentration of 16% at sea level is necessary.

• Fuel sources are abundant in forest fires; even buried trash can serve as combustible material during dry summer months.

Triangle of Fire

• To create fire, three elements must be present: fuel, heat (e.g., lightning or matches), and oxygen. Machines like chainsaws can also generate sufficient heat for ignition.

Chemical Reactions in Fire

• Chemical reactions leading to combustion are more common than perceived. An example includes the ignition process when striking a match.

Match Composition and Ignition Process

• Modern matches use red phosphorus instead of toxic white phosphorus. The head contains potassium chlorate among other compounds designed for controlled burning.

Energy Release During Ignition

• Heat generated from friction ignites the match head's chemicals, initiating combustion through the release of energy from potassium chlorate.

Chain Reaction in Fires

• For sustained combustion leading to wildfires, conditions must allow for continuous formation of new fire triangles through chain reactions.

Elements Supporting Fire Dynamics

• The four essential elements for sustaining fire include fuel, oxidizing agent (oxygen), heat source, and the chain reaction itself which perpetuates further reactions leading to uncontrolled fires.

Characteristics of Fuels

Understanding Combustion and Its Components

The Basics of Combustion

• Combustion involves vapors produced through pyrolysis; gaseous fuels do not require vaporization or pyrolysis due to their state.

• Oxygen, typically found in the air at 21% concentration at sea level, is crucial for combustion. A minimum of 16% oxygen is necessary for combustion to occur.

• Opening doors or windows during a confined fire can dangerously introduce oxygen, potentially leading to explosions.

Key Elements of Combustion

• Heat must come from a competent source; it provides the minimum thermal energy needed to ignite combustible gases and sustain combustion.

• The reaction chain in combustion consists of complex chemical reactions that lead to rapid oxidation of fuel, resulting in self-sustaining fires.

Types of Fires and Their Characteristics

• Different types of fires (e.g., forest fires vs. confined space fires) have unique characteristics based on the materials involved.

• Combustion is an exothermic reaction involving rapid oxidation, producing light and heat. Solid and liquid fuels vaporize before burning.

Byproducts of Combustion

• Gas combustion usually produces visible flames; however, some liquid combustibles may burn without visible flames.

• The chemical reaction in combustion can be represented by the breakdown of cellulose and lignin in wood during forest fires.

Environmental Impact and Safety Concerns

• Forest fire combustion generates CO2, water vapor, light, heat, nitrogen compounds, carbon monoxide, hydrogen gas, and soot.

• Carbon residue from smoke can conduct electricity when near high-tension power lines, posing risks such as electric shocks.

Energy Output from Combustion

• The calorific value generated averages around 3600 kilocalories; only about 15% contributes directly to heating surrounding air.

Phases of Combustion Process

• Preheating occurs below 100 degrees Celsius where moisture evaporates from wood. This phase produces white smoke.

Distillation Phase

Combustion Phases and Temperature Effects

Understanding the Initial Phase of Combustion

• The application of direct heat to wood does not guarantee a specific combustion outcome; rather, external heat through radiation initiates vaporization at around 100 degrees Celsius.

• Scientific studies indicate that certain fine fuels can combust effectively at temperatures as low as 270 degrees Celsius.

Transitioning Through Combustion Stages

• As temperatures approach 300 degrees Celsius, carbon monoxide begins to form, marking the transition into charcoal production with an energy release exceeding 300 calories per kilogram of fuel.

• Between 350 and 500 degrees Celsius, combustion continues with visible blue smoke indicating efficient burning conditions.

Advanced Combustion Dynamics

• Temperatures can escalate up to 1000 degrees Celsius during combustion; this phase is characterized by significant energy release and gas formation.

• The third phase of combustion occurs between 500 and 800 degrees Celsius, where temperature fluctuations lead to varying rates of heat release.

Observations from Experimental Video

• A video recorded in a controlled environment demonstrates real-time temperature changes during a fire scenario, highlighting the pre-drying phase at around 100 degrees Celsius.

• The video shows how combustible gases begin forming as temperatures rise above the initial threshold.

Fire Management Techniques

• In practical applications, water is continuously applied during high-temperature scenarios (up to nearly 900 degrees), showcasing firefighting strategies against intense fires.

• The effectiveness of water application in managing large-scale fires is illustrated by its ability to cool down flames within seconds while maintaining high temperatures.

Spontaneous Combustion Explained

Mechanisms Behind Spontaneous Combustion

• Spontaneous combustion arises from auto-heating processes due to biological reactions involving fungi and bacteria that generate internal heat.

Chemical Reactions Leading to Fire Risks

• Auto-heating starts with exothermic reactions occurring internally within organic materials like sawdust or coal piles when they reach approximately 75 degrees Celsius.

Heat Retention Challenges

Factors Influencing Fire Behavior

Importance of Ambient Temperature

• The ambient temperature at the start of a fire pile is crucial; research indicates that higher temperatures can lead to quicker ignition, potentially within weeks or even months.

Role of Pile Volume and Shape

• The volume and shape of the fire pile affect the speed of exothermic reactions. This is closely linked to the type of combustible material present.

Thermal Runaway Process

• Poor heat conductivity in materials can cause internal temperatures to rise significantly, leading to incandescent conduction and flame-free combustion.

Awareness Among Workers

• Many forest workers are unaware of smoldering fires until disturbed by machinery, which introduces oxygen and ignites flames.

Understanding Fire Structure

Components of a Fire

• For effective firefighting, understanding fire structure is essential. Fires consist of various parts: head (front), left flank, right flank, and tail.

Influence of Wind on Fire Spread

• The direction and strength of wind significantly influence how fires spread; sometimes they behave unpredictably regardless of local wind conditions.

Firefighting Strategies

Grid System for Fire Management

• Firefighters use a grid system to subdivide areas affected by fire for safer operations. Certain quadrants are designated as no-go zones for safety reasons.

Identifying Points of Origin

• Quadrants 3 and 4 are often where initial points of ignition are found due to unburned fuels reigniting under changing wind conditions.

Heat Transfer Mechanisms in Fires

Initiation through Heat Transfer

• Fires require external heat sources that transfer energy into combustible materials, leading to pyrolysis—a chemical process that produces flammable gases necessary for combustion.

Methods of Heat Transfer

• Heat can be transferred via conduction, convection, or radiation. Conduction involves direct contact between materials allowing heat flow from hot to cold areas.

Subterranean Combustion Dynamics

Underground Fires

• Subterranean fires can occur without air presence; nitrogen compounds decompose under heat releasing oxygen and carbon monoxide, sustaining combustion underground.

Understanding Fire Propagation Mechanisms

The Role of Heat Transmission in Wildfires

• The phenomenon of heat transmission through roots continues combustion, leading to new fires days later. This highlights the persistence of fire even after initial flames are extinguished.

• Convection plays a crucial role in wildfires; hot air rises, and if wind is present, it pushes this heated air forward, drying nearby fuel and accelerating combustion.

• Fresh air intake is vital for combustion; it oxygenates the fire. Radiation also contributes by transferring heat directly through electromagnetic waves from sources like the sun or a campfire.

Understanding Radiation and Its Impact

• Heat transfer via radiation occurs in straight lines as electromagnetic waves. The intensity of radiation decreases with distance from the heat source, affecting how much fuel can be ignited.

• The amount of heat transmitted from a material is proportional to its absolute temperature. Doubling energy can increase radiative heating significantly (up to 16 times), indicating radiation's potency.

• While convection is more influential than radiation in most wildfire scenarios, radiation primarily affects fires moving downhill by heating lower fuels.

Fire Behavior on Slopes

• When a fire descends a slope, convection effects diminish since it's moving over already burned areas. Instead, downward radiation becomes more significant but slower compared to upward convection.

• Fires climbing slopes propagate faster due to combined effects of conduction, convection, and secondary ignition points created by embers carried by wind or gravity.

Secondary Ignition Sources

• Secondary ignition can occur when small burning particles travel from one fire to ignite another area. These embers can be transported by wind or animals.

• Strong winds can lift burning debris and carry it far distances, potentially starting new fires when these materials land on combustible surfaces below.

Unique Cases of Fire Initiation

• An example illustrates how rising hot air currents can carry small ignited materials that may lead to new fires elsewhere due to their elevated transport mechanism.

• Gravity plays a role in fire spread; falling debris can ignite lower vegetation as it descends down slopes during intense conditions.

Electrical Causes of Wildfires

• A notable case involved an electrical incident where an electrified bird fell and started a fire upon contact with dry ground—demonstrating unexpected ignition sources in wildfires.

• Birds can catch fire mid-flight due to electrical interactions or collisions with power lines—this phenomenon has been documented frequently in regions like the U.S., emphasizing the need for awareness regarding wildlife interactions with infrastructure.

Propagation Speed Considerations

Understanding Fire Propagation Dynamics

Key Concepts of Fire Propagation

• The speed of line propagation is not just about how fast the fire moves forward; it also includes the direction of the fire's head, measured in meters per minute or kilometers per hour. Surface preparation speed measures the growth of burned area in square meters per minute or hectares per hour.

• Perimeter propagation measures the increase in perimeter length, expressed similarly in meters per minute or kilometers per hour. Linear propagation is defined as movement measured in these same units.

• Speed categories for fire propagation are established:

• Slow: <120 m/h

• Medium: 120-600 m/h

• High: 600-2400 m/h

• Very High: 2400-4200 m/h

• Extreme: >4200 m/h.

Factors Influencing Fire Behavior

• The average speeds mentioned are based on recorded data; however, fires can advance at rates exceeding 40 km/h depending on environmental factors such as fuel type, ambient temperature, humidity levels, and wind speed.

• At extreme speeds (e.g., >4200 m/h), fire behavior becomes comparable to a person walking quickly through a forest—this indicates an alarming rate of spread that poses significant risks.

Understanding Firestorms and Combustion

• Discussion shifts towards direct fires and firestorms, with references to historical large-scale wildfires from years past (e.g., 2017). A guest speaker will provide insights into wildfire research during the next class.

• Generalized combustion occurs when all available fuel ignites simultaneously due to radiation from flames and hot gas transport via convection. This phenomenon is exacerbated by current issues like drought and global warming.

Environmental Conditions Impacting Fires

• Rising temperatures due to climate change could significantly alter conditions for wildfires, especially in regions previously less affected by such disasters. Awareness is crucial as wildfire season approaches.

Triangle of Fire Behavior Factors

• The development of a wildfire depends on three main factors:

• Availability of combustible materials.

• Atmospheric conditions including humidity over time.

• Topography which influences how fires spread across landscapes.

Classification of Combustibles

• Combustibles are classified based on their nature (living vs. dead), structure (heavy vs. light), and caloric intensity—the greater the caloric intensity, the higher potential for destruction during a fire event.

• Different types of combustibles include:

• Surface Fuels: Leaves, branches, shrubs found at ground level.

• Aerial Fuels: Materials extending from ground level up to tree canopies.

• Subterranean Fuels: Roots and buried debris that can ignite underground.

Continuity and Quantity of Fuel Sources

• Fuel continuity refers to horizontal proximity among combustible materials which affects how easily a fire spreads across terrain. Vertical continuity allows flames to climb from lower branches to tree tops—this transition can lead to crown fires that are difficult to control.

• Quantitative classifications indicate varying amounts of fuel present:

• Grasslands may have between 2–12 tons/hectare.

• Thinning waste could reach up to 70 tons/hectare.

• Heavily vegetated areas might contain between 20–100 tons/hectare.

Understanding Fire Behavior and Fuel Types

The Role of Policies in Combustion

• Discussion on the importance of policies related to fire prevention, particularly concerning fuel management.

Characteristics of Vegetation and Fuels

• Introduction to various plant species like Chilean pine (pino insigne) and eucalyptus, which contain numerous chemical substances affecting combustion.

• Ongoing debate about the combustibility of pino insigne compared to other species; it is noted that these trees can lead to faster combustion rates.

Classification of Fuels by Size

• Overview of fuel classification based on size:

• Fine fuels: less than 5 mm

• Regular fuels: 5 to 25 mm

• Medium fuels: 25 to 75 mm

• Coarse fuels: greater than 75 mm

Moisture Content and Delay Time in Fuels

• Explanation of "delay time," which refers to how long dead fuel takes to gain or lose moisture until reaching equilibrium with the environment.

• Example provided for fine fuels like dry grass, which can reach a critical moisture loss within one hour under sunlight conditions.

Types of Wildfires Based on Propagation

• Classification of wildfires into three types:

• Surface fires: burn through materials at ground level.

• Subterranean fires: occur below the surface, often difficult to detect.

• Crown fires: spread through the tops of trees, posing significant challenges for control due to their speed and intensity.

Impact of Weather Conditions on Fire Behavior

• Introduction to atmospheric conditions as a crucial factor influencing fire behavior; distinguishes between weather (short-term state) and climate (long-term patterns).

• Key variables affecting fire behavior include air temperature, humidity, and wind speed. These factors significantly influence ignition and propagation rates.

Wind's Influence on Fire Dynamics

• Discussion on different types of winds impacting fire behavior:

• General winds: large-scale air movements across regions.

• Local winds: smaller scale effects that can change rapidly.

Understanding Local Winds and Their Impact on Forest Fires

General Wind Patterns in Chile

• The general wind patterns in Chile, particularly during summer, are dominated by southern and southwestern winds. These winds arise from cold air masses replacing warm air that rises.

• Most forest fires in Chile typically propagate from south to north along the coast, with a general west-to-east spread observed.

Types of Local Winds

• Local winds differ from general winds as they occur over smaller areas and result from the vertical movement of air masses at varying temperatures influenced by terrain.

• Two main types of local winds include valley winds (which ascend during the day due to heating) and slope winds (which descend at night as temperatures drop).

Behavior of Fire-Induced Winds

• Fires generate erratic and turbulent local winds due to heated air rising through convection columns, drawing in cooler air from nearby valleys.

• Valleys act like chimneys for these fires, creating unpredictable fire behavior that poses significant risks for firefighting efforts.

Risks Associated with Local Winds

• When fires spread into valleys, there is a high risk for firefighters as escape routes can become blocked; past incidents have highlighted this danger.

• A specific type of warm wind known as "east component" can lead to rapid temperature increases and decreased humidity levels, exacerbating fire conditions.

Characteristics of East Component Winds

• This east component wind can produce gusty conditions exceeding 20 km/h (up to 70 km/h), significantly impacting fire behavior across different regions in Chile.

• Various names exist for this phenomenon globally: "foehn" in Europe, "chinook" in North America, and "Santa Ana" winds in California—all associated with dry conditions conducive to wildfires.

Effects on Weather Patterns

• The east component wind leads to reduced humidity levels which can last several days; it has been linked to severe wildfire outbreaks historically noted on February 11, 2019.

• As moist air ascends over mountains (barlovento), it cools down leading to precipitation while the descending dry air (sotavento side) warms up rapidly—creating ideal conditions for wildfires.

Incendios Intencionales y su Impacto

Contexto de los Incendios

• Se menciona que no se está pernoctando en el área debido a un aumento de incendios, lo que generó sospechas sobre la posibilidad de atentados coordinados.

• Se discute la teoría de que las condiciones climáticas (viento, temperatura y humedad) pueden contribuir a la generación de incendios, sugiriendo que algunas personas podrían estar iniciándolos intencionalmente.

Observaciones en el Lugar del Incendio

• Un incendio comenzó cerca de una casa ubicada junto a árboles; afortunadamente, no se produjo un daño significativo en la vivienda gracias a la intervención oportuna.

• Una residente observó humo y llamas iniciales del incendio mientras regaba su jardín. Notó la presencia de dos jóvenes con capuchas, lo cual despertó sus sospechas sobre su posible implicación en el inicio del fuego.

Investigación y Resultados

• La investigación reveló que el incendio fue intencional. Carabineros también realizaron indagaciones al respecto.

• Se identificaron seis balones de gas en una instalación cercana al lugar donde comenzó el incendio. A pesar del riesgo potencial, no hubo explosiones ni daños mayores.

Dinámica del Incendio

• En otra ocasión, un nuevo incendio se generó por condiciones similares durante la noche. Aunque inicialmente tuvo poca intensidad, resurgió al día siguiente debido al calor solar.

• El fenómeno conocido como "potencial de retorno" permitió que el fuego reavivara áreas previamente quemadas debido a combustible residual no consumido completamente.

Testimonios y Consecuencias

• Testigos afirmaron haber visto a varias personas encender fogatas antes del inicio del incendio. Esto indica una posible conexión entre estas acciones y los incendios posteriores.

• Aproximadamente 22 hectáreas fueron afectadas por los incendios; se mencionan imágenes impactantes relacionadas con las columnas de llamas generadas por estos eventos.

Formación de Nubes Convectivas

• Se explica cómo las intensas temperaturas provocan aire caliente y humo, formando nubes cumulonimbus capaces de generar tormentas eléctricas.

• Este fenómeno puede resultar en rayos que inician nuevos incendios; se hace referencia a incidentes pasados en California donde múltiples incendios fueron causados por este tipo de actividad atmosférica.

Conclusión sobre el Comportamiento del Fuego

• La naturaleza impredecible e incontrolable de los incendios forestales es destacada debido a las condiciones climáticas cambiantes y actividades humanas irresponsables.

Understanding the Influence of Wind and Topography on Wildfire Propagation

The Role of Wind in Fire Spread

• New wildfires are increasingly influenced by global warming, highlighting the urgency of understanding fire dynamics.

• Wind plays a critical role in fire propagation; stronger winds lead to faster spread, particularly in non-flat terrains.

• The direction and speed of wind can significantly affect the linear propagation rate of fires, with higher wind speeds accelerating flame movement towards combustible materials.

Topography's Impact on Fire Behavior

• Topography encompasses physical characteristics of terrain that influence wildfire behavior; it is a constant factor unlike fuel types which can change.

• Terrain configuration affects local wind patterns, creating variations such as upslope and downslope winds that modify fire dynamics.

Understanding Slope and Its Effects

• Slope is defined as the degree of elevation change over horizontal distance; steeper slopes can dramatically increase fire spread rates.

• A 30% slope can double the speed of fire propagation, while a 55% slope may quadruple it due to enhanced airflow from heated air rising.

The Importance of Exposure

• Exposure refers to the orientation of slopes concerning cardinal directions; south-facing slopes receive more direct sunlight, leading to drier conditions and potentially faster combustion rates compared to north-facing slopes.

Ecological Impact of Forest Fires

Factors Influencing Fire Behavior

• The southern regions experience slower fire initiation due to higher humidity and more fuel availability compared to the northern slopes, highlighting the importance of topography in fire dynamics.

• Humidity levels in dead light fuels vary significantly; even with high ambient temperatures, shaded areas (umbría) retain more moisture than sunlit areas (solana), affecting combustion rates.

Ecological Consequences of Fire Suppression

• Firefighting efforts often involve fluorinated surfactants that can cause severe environmental damage and irreversible genetic changes in wildlife, alongside ozone depletion.

• A paradox arises where effective firefighting leads to increased accumulation of forest biomass, creating a greater risk for future fires despite immediate suppression success.

Emissions and Environmental Degradation

• Each hectare of burning forest can release 80 to 100 tons of particulate matter and significant greenhouse gases, contributing massively to atmospheric CO2 levels.

• During a specific period in early 2017, approximately 100 million tons of CO2 were released into the atmosphere from wildfires, equating to total emissions from the previous year.

Biodiversity at Risk

• The loss of forest cover leads to soil degradation, erosion, desertification, and threatens various ecosystems and species such as the endangered "monito del monte," a marsupial native to Chile.

Importance of Biodiversity Conservation

• Protecting biodiversity is crucial not only for ethical reasons but also for human survival; it ensures clean air and water while facilitating nutrient recycling essential for food production.

Future Outlook on Climate Change

• Despite efforts made today towards conservation or climate change mitigation, there is skepticism about reversing global warming trends; humanity may face its fifth mass extinction if current patterns continue.

Conclusion & Call for Action

Photo Capture and Real Smiles

Discussion on Capturing Moments

• The speaker mentions taking a screenshot, indicating the importance of capturing moments visually.

• There is an emphasis on authenticity, as the speaker refers to "real smiles," suggesting a focus on genuine expressions in photography.