The APIE Response Model and Hazardous Materials Characteristics

The APIE Response Model

• The APIE response model is a structured four-step problem-solving process used by first responders to manage hazardous materials incidents.

• Step One: Analyze the Incident

  • During this initial phase, personnel and responders attempt to gain a comprehensive understanding of the current situation.

  • Responders identify specific factors, including:

    • The specific hazardous materials (hazmat) involved.

    • The types of containers present at the scene.

    • The quantity of materials released or potentially released.

    • The number of exposures (people, property, or environment).

    • Potential hazards associated with the specific substances.

    • Any other relevant information required to plan a safe and effective response.

• Step Two: [Planning]

  • Note: Due to a data error in the source material, the explicit description of Step Two is omitted; however, it involves the determination of tasks to be performed based on the analysis from Step One.

• Step Three: Implementation

  • In this phase, responders perform the specific tasks and tests determined during the planning stage.

• Step Four: Evaluate Progress

  • This phase begins during the response and continues throughout the incident until final termination.

  • Responders monitor the situation to determine if the response plan is working effectively or if adjustments are necessary.

• Responder Responsibilities

  • Awareness-level and operations-level responders generally have responsibilities distributed across the analysis, planning, and implementation phases.

Definition and Causes of Hazardous Materials Incidents

• Hazardous Material Incident Definition

  • An emergency involving a substance that poses an unreasonable risk to people, the environment, and/or property.

  • Incidents may involve a substance released from its container or a substance that is currently on fire.

• Common Causes of Incidents

  • Human error.

  • Mechanical breakdown or malfunctions.

  • Container failures.

  • Transportation accidents.

  • Deliberate acts (e.g., chemical suicides and Weapons of Mass Destruction/WMD incidents).

Health Effects and Routes of Entry

• Health Effects

  • Acute Health Effects: Short-term effects that appear within hours or days of exposure. Examples include vomiting or diarrhea.

  • Chronic Health Effects: Long-term effects that may take years to manifest. A primary example is cancer.

• Routes of Entry

  • Inhalation: Breathing hazardous materials in through the nose or mouth.

  • Ingestion: Eating or swallowing hazardous materials through the mouth.

  • Absorption: The process of taking in materials through the skin or the eyes.

  • Injection: The process of taking in materials through a puncture or break in the skin.

Mechanisms of Harm

• There are three primary mechanisms by which hazardous materials cause harm:

  1. Corrosivity: The ability of chemicals to destroy or burn living tissue. Corrosives can hurt responders upon contact with the body and can also cause significant damage to tools and equipment.

  2. Toxicity: The degree to which a substance causes harm once inside the body.

  3. Energy Release: This often presents the greatest threat at a hazmat incident. Energy can be released due to chemical or physical properties, shipping methods, or storage conditions.

• Types of Energy Release to Monitor:

  • Heat.

  • Mechanical energy.

  • Pressure.

  • Electricity.

  • Chemical energy.

  • Radiation.

Physical States of Matter

• Gases

  • Characterized by an indefinite shape.

  • Expand rapidly and travel quickly and easily.

  • May rise or sink in the air depending on density.

  • May displace oxygen in an enclosed space.

  • Gases are difficult to contain for mitigation purposes.

  • Compressed and liquefied gases expand rapidly when released, potentially threatening large geographic areas.

  • Invisible or odorless gases may require specialized detection equipment, such as a combustible gas detector, for identification.

• Liquids

  • Tend to pool, form streams, or flow downhill.

  • May sink or float when they enter water.

  • Likely to release vapors that behave similarly to gases.

• Solids

  • The least mobile of the three states of matter.

  • They typically stay in place unless moved by exterior forces such as wind, water, gravity, or other forces.

  • Tiny solid particles may stay suspended in the air and can cause entrapment hazards.

  • Some solids are highly reactive.

Physical Properties of Hazardous Materials

• Definition: Characteristics that do not involve the chemistry or chemical nature of the material. They describe how a material behaves regarding physical influences (temperature, pressure) or when compared to/mixed with other materials.

• Vapor Pressure: The pressure exerted by a saturated vapor above its own liquid in a closed container; it is the pressure produced by the vapors released by the liquid.

• Boiling Point: The temperature at which a liquid changes to a gas at a given pressure, usually expressed in degrees Fahrenheit at sea level pressure.

• Melting Point: The temperature at which a solid substance changes into a liquid state at normal atmospheric pressure.

• Freezing Point: The temperature at which a liquid becomes a solid at normal atmospheric pressure.

• Vapor Density: The weight of a given volume of pure vapor or gas compared to the weight of an equal volume of dry air at the same temperature and pressure.

  • \text{Vapor Density} < 1: Indicates the vapor is lighter than air and will rise.

  • \text{Vapor Density} > 1: Indicates the vapor is heavier than air and will sink.

  • Common materials with a vapor density greater than $1$ include:

    • Propane.

    • Hydrogen sulfide.

    • Ethane.

    • Butane.

    • Chlorine.

    • Sulfur dioxide.

• Solubility and Miscibility

  • Solubility in Water: Expressed as the percentage of a material by weight that will dissolve in water at ambient temperatures.

  • Miscibility: Describes the ability of two or more gases or liquids to mix with or dissolve into each other in any proportion. Materials that do not readily dissolve in each other are considered immiscible.

• Specific Gravity: The ratio of the density (mass per volume) of a material to the density of a standard material (usually an equal volume of water at standard conditions).

• Persistence: The ability of a chemical to remain in the environment. Persistent nerve agents remain effective at the point of dispersion for much longer than non-persistent agents.

• Viscosity: A measure of the thickness or flowability of a liquid at a given temperature. Higher numerical values indicate higher viscosity (thicker liquid). Viscosity is greatly affected by temperature; typically, the hotter the liquid, the thinner/more fluid it becomes.

Chemical Properties and Flammability

• Definition: Properties that describe the chemical nature of a material and behaviors occurring at the molecular level.

• Flammability Factors

  • Flash Point: The minimum temperature at which a liquid or volatile solid gives off sufficient vapors at its lower explosive limit to form an ignitable mixture with air near the surface. At this point, the material will flash in the presence of an ignition source but will not continue to burn.

  • Autoignition Temperature: Also known as the ignition temperature; the minimum temperature to which the fuel in the air must be heated to initiate self-sustained combustion without an independent ignition source.

  • Flammable (Explosive/Combustible) Range: The percentage of gas or vapor concentration in air that will burn or explode if ignited.

    • Lower Explosive Limit (LEL) / Lower Flammable Limit (LFL): The lowest concentration of vapor/gas that will burn.

    • Upper Explosive Limit (UEL) / Upper Flammable Limit (UFL): The highest concentration of vapor/gas that will burn.

Corrosivity: Acids and Bases

• Corrosives are categorized into two types based on the pH scale (ranging from $0$ to $14$):

• Acids

  • Any chemical that ionizes to yield hydrogen ions in water.

  • pH Range: $0$ to $6.9$.

  • Can cause severe chemical burns to flesh and permanent eye damage.

• Bases

  • A water-soluble compound that chemically dissociates in water to form a negatively charged hydroxide.

  • pH Range: $7.1$ to $14$.

  • Bases react with acids to form a salt by releasing an unshared pair of electrons or receiving a proton.

  • Bases break down fatty skin tissues and can penetrate deeply into the body.

Chemical Reactivity and Polymerization

• Chemical Reactivity: The relative ability of a substance to undergo a chemical reaction with itself or other materials. These reactions can result in pressure build-up, temperature increases, or the formation of corrosive, toxic, or noxious byproducts.

• Reactive Materials

  • May react vigorously with air, water, heat, light, or other materials.

  • Low activation energy: Reactions that require very little help to begin.

  • Water Reactive: Materials that react with water at room temperature because ambient temperature is sufficient to provide the required activation energy.

• Oxidation

  • The oxidizing agent in the reactivity triangle provides the oxygen necessary for the reaction.

  • Strong oxidizers encourage intense reactions.

  • Higher concentrations of oxygen result in hotter oxidation reactions.

• Polymerization

  • A chemical reaction where simple molecules combine to form long-chain molecules.

  • Catalyst: A substance that increases the rate of polymerization while decreasing the activation energy needed for the reaction to continue.

  • Inhibitors: Materials added to products that easily polymerize to control or prevent undesired reactions and maintain stability.