Fundamentals of Fire Fighter Skills, Third Edition
Chapter 29: Hazardous Materials: Properties and Effects
Chief Concepts
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The first step in understanding the hazard posed by a substance involves identifying its
state of matter: solid, liquid, or gas.
A physical change occurs when a substance is subjected to outside influences such as
heat, cold, or pressure. For example, when water is exposed to cold, it becomes ice. A
chemical change is a change in the substance’s chemical makeup with a release of some
form of energy. For example, if oxygen is removed from water (H2O), the chemical
makeup of the substance changes (H).
The boiling point is the temperature at which a liquid eventually turns to gas. Flammable
liquids with low boiling points are dangerous because of their potential to produce large
volumes of flammable vapor when exposed to relatively low temperatures.
The three aspects to consider when evaluating the fire potential of a chemical are the
following:
• Flash point: An expression of the temperature at which a liquid fuel gives off
sufficient vapor that, when an ignition source is present, results in a flash fire.
• Ignition temperature: When a liquid fuel is heated beyond its ignition temperature,
the substance ignites without an external ignition source.
• Flammable range: A mixture of fuel and air, defined by upper and lower
flammable limits, that reflects an amount of vapor mixed with a volume of air.
The wider the flammable range, the more dangerous the material.
When operating in any environment where a flammable or combustible vapor cloud is
suspected to be present, always err on the side of safety and assume that the danger of
ignition exists.
In addition to addressing the flammability of a particular vapor or gas, fire fighters must
determine the vapor density (or weight) of the substance. To find a chemical’s vapor
density, consult a reference source such as the MSDS.
In the absence of reliable reference sources in the field, fire fighters can use the HA HA
MICEN mnemonic to remember a number of lighter-than-air gases:
H: Hydrogen
A: Acetylene
H: Helium
A: Ammonia
M: Methane
I: Illuminating gas (neon and hydrogen cyanide)
C: Carbon monoxide
E: Ethylene
N: Nitrogen
The key point to understanding vapor pressure is this: The vapors released from the
surface of the liquid must be contained if they are to exert any pressure. Essentially, the
liquid inside a container will vaporize until the molecules given off by the liquid reach
equilibrium with the liquid itself. It is a balancing act between the liquid and the vapors
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in which some liquid molecules turn into vapor, even as other molecules leave the vapor
phase and return to the liquid phase.
Always remember that when dealing with chemical emergencies water might not always
be the best and safest choice to mitigate the situation. It is a tremendously aggressive
solvent and has the ability to react violently with certain other chemicals.
Corrosivity is the ability of a material to cause damage to the body on contact. Corrosives
constitute a complex group of chemicals and fall into two classes: acids and bases. Acids
have pH values less than 7. Bases have pH values greater than 7. Generally, substances
with pH values of 2.5 and lower and 12.5 and higher are considered to be strong.
Radiation is the energy transmitted through space in the form of electromagnetic waves
or energetic particles. It can be described as ionizing or non-ionizing. Ionizing radiation
has the potential to ionize an atom or molecule through atomic interactions. Non-ionizing
radiation does not carry enough energy to remove an electron from an atom or molecule.
Radiation is everywhere and has been around since the beginning of time. For the most
part, the health hazards posed by radiation are a function of two factors:
• The amount of radiation absorbed by the body has a direct relationship to the
degree of damage done.
• The amount of exposure time ultimately determines the extent of the injury.
Fire fighters can protect themselves from alpha particle exposure by wearing HEPA
filters. Fire fighters can protect themselves from beta particle exposure by wearing
SCBA. Structural firefighting gear and SCBA do not protect fire fighters from gamma
rays.
The residue from a chemical is contamination. Secondary contamination occurs when a
person or object transfers the contamination to another person or object by direct contact.
To prevent this, decontamination is necessary.
The seven categories of WMD are as follows:
• Thermal: Heat created from intentional explosions or fires, or cold generated by
cryogenic liquids.
• Radiological: Radioactive contamination from dirty bombs; alpha, beta, and
gamma radiation.
• Asphyxiation: Oxygen deprivation caused by materials such as nitrogen; tissue
asphyxiation from blood agents.
• Chemical: Injury and death caused by the intentional release of toxic industrial
chemicals, nerve agents, vesicants, poisons, or other chemicals.
• Etiological: Illness and death resulting from biohazards such as anthrax, plague,
and smallpox; hazards posed by bloodborne pathogens.
• Mechanical: Property damage and injury caused by explosion, falling debris,
shrapnel, firearms, explosives, and slips, trips, and falls.
• Psychogenic: The mental harm from being potentially exposed to, contaminated
by, and even just being in close proximity to an incident of this nature.
Nerve agents attack the body’s central nervous system. The signs and symptoms of nerve
agent exposure can be remembered through the mnemonic SLUDGEM:
S: Salivation
L: Lachrymation (tearing)
U: Urination
D: Defecation
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G: Gastric disturbance
E: Emesis (vomiting)
M: Miosis (constriction of the pupil)
Blister agents include sulfur mustard and Lewisite. Immediate skin decontamination is
required.
Cyanide compounds prevent the body from using oxygen. The typical signs and
symptoms include vomiting, dizziness, watery eyes, and deep and rapid breathing.
Choking agents are mostly designed to incapacitate rather than to kill. Irritants can be
dispersed to briefly incapacitate a person or groups of people.
Convulsants are capable of causing seizures. They include nerve agents such as sarin,
soman, and VX. It is critical to identify their presence and avoid exposure.
The four ways that chemicals enter the body are the following:
• Inhalation: Through the lungs
• Absorption: By permeating the skin
• Ingestion: By the gastrointestinal tract
• Injection: Through cuts or other breaches in the skin
A chronic health hazard is an adverse health effect that occurs gradually over time. Acute
health effects occur after only relatively short exposure periods.
One of the most frequently consulted hazardous materials references used by emergency
response agencies is the Emergency Response Guidebook (ERG). It is designed to
provide basic information to keep both responders and the general public safe during the
initial stages of a hazardous materials incident. The ERG is divided into four major
sections, plus some additional reference materials:
• Yellow section: Lists hazardous materials in numerical order by the chemical
identification number.
• Blue section: Lists hazardous chemicals in alphabetical order.
• Orange section: Provides basic response information for specific groups of
chemicals.
• Green section: Provides information on the evacuation/ isolation distance for
specific chemicals.
• White pages: List reference resources, including who to call for assistance,
placarding information, rail and highway vehicle identification charts, and a
glossary of key terms.
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