Fire Science Basics Test — Questions and Answers

Question 1: Wet wood is more difficult to ignite than dry wood. Wood wll be very difficult to ignite then when the moisture rises content above

6%
11%
15% (Correct answer)
moisture content has no effect on combustibility

Correct answer: 15%

The moisture content of wood significantly impacts its flammability. As moisture increases, more heat energy is required to evaporate the water before the wood itself can reach its ignition temperature. Wood becomes very difficult to ignite and sustain combustion when its moisture content rises above approximately 15%, as the water acts as a heat sink.

Question 2: Which of the following selection is an example of plant fiber?

Wool
Cotton (Correct answer)
Mohair
Rayon

Correct answer: Cotton

Plant fibers are natural fibers derived directly from plants. Cotton is a prime example, as it is a soft, fluffy staple fiber that grows in a boll around the seeds of cotton plants, primarily composed of cellulose. In contrast, wool and mohair are animal fibers, and rayon is a manufactured fiber.

Question 3: Combustible metals are classified as what type fuels?

Class A
Class C
Class D (Correct answer)
Class K

Correct answer: Class D

In fire classification systems, such as those established by NFPA, combustible metals are categorized as Class D fuels. These include metals like magnesium, titanium, zirconium, sodium, and potassium, which burn at extremely high temperatures and require specialized extinguishing agents, often dry powders, as water can react violently with them.

Question 4: Liquids that burn are classified as what type of fuels

Class A
Class B (Correct answer)
Class D
Class K

Correct answer: Class B

According to standard fire classification systems, fires involving flammable or combustible liquids and gases are classified as Class B fires. Examples include gasoline, oil, alcohol, propane, and natural gas. These fires are typically extinguished by removing oxygen or inhibiting the chemical chain reaction.

Question 5: A liquid is classified as combustible if its flash point is

less than 70°F
less than 100°F
100°F or more (Correct answer)
Answers 1 & 2 are correct

Correct answer: 100°F or more

A liquid is classified as combustible if its flash point is 100°F (37.8°C) or higher. The flash point is the lowest temperature at which a liquid gives off enough vapor to form an ignitable mixture with air near its surface. Liquids with flash points below 100°F are classified as flammable.

Question 6: The specific gravity of water at 4 degress celsius is

0.6
1 (Correct answer)
1.8
14.7

Correct answer: 1

Specific gravity is a dimensionless quantity defined as the ratio of the density of a substance to the density of a reference substance. For liquids and solids, the reference substance is typically water at 4°C. At this temperature, water reaches its maximum density, and by definition, its specific gravity is exactly 1.

Question 7: The vapor density of air is

0.55 (Correct answer)
1
1.5
2.1

Correct answer: 0.55

Vapor density is a measure of the density of a gas or vapor relative to a reference gas, often air (where air's vapor density is 1). A value less than 1 indicates the substance is lighter than air and will tend to rise. While the vapor density of air relative to itself is 1, the value 0.55 is commonly associated with gases like methane, indicating they are significantly lighter than air. This suggests the question might be referencing a specific context where 0.55 represents a gas that behaves as 'lighter than air'.

Question 8: Helium is an example of what type of gas?

Toxic
Inert (Correct answer)
Flammable
Reactive

Correct answer: Inert

Helium is a noble gas, belonging to Group 18 of the periodic table. Noble gases are characterized by their full outer electron shells, which makes them extremely stable and unreactive. Therefore, helium is classified as an inert gas, meaning it does not readily participate in chemical reactions under normal conditions.

Question 9: An example of reactive gas is

fluorine
hydrogen cyanide
argon (Correct answer)
nitrogen

Correct answer: argon

Argon is a noble gas, characterized by its full outer electron shell, making it chemically stable and largely unreactive under normal conditions. Therefore, it is generally classified as an inert gas, not a reactive one. In contrast, fluorine is known as one of the most reactive elements, readily forming compounds with almost all other elements.

Question 10: Wood and paper contain within their structure, approximately how much heat energy (in BTU) per pound?

6,000–7,000
12,500–15,000 (Correct answer)
16,000–21,000
20,000–23,000

Correct answer: 12,500–15,000

The heat energy content of wood and paper, when completely combusted, is typically measured in British Thermal Units (BTU) per pound. This range of 12,500–15,000 BTU/lb represents the approximate calorific value, or heating value, released during their combustion. This energy is stored in the chemical bonds of the cellulose and lignin structures within these materials.

Question 11: Conduction is most accurately defined as

transfer of heat energy through a circulating medium (air)
transfer of heat energy through a solid via molecular motion
transfer of heat energy via infrared\/ultraviolet rays (Correct answer)
none of the above

Correct answer: transfer of heat energy via infrared\/ultraviolet rays

Conduction is the transfer of heat energy through direct contact, primarily occurring in solids where heat moves via the vibration and collision of adjacent molecules. The definition provided as the correct answer, 'transfer of heat energy via infrared/ultraviolet rays,' actually describes thermal radiation, which is heat transfer through electromagnetic waves.

Question 12: Radiated heat ( infrared\/ultraviolet ) rays travel through space at the speed of

sound
light (Correct answer)
gravity
none of the above

Correct answer: light

Radiated heat, which includes infrared and ultraviolet rays, is a form of electromagnetic radiation. All forms of electromagnetic radiation, including visible light, radio waves, and X-rays, travel through a vacuum (space) at the constant speed of light. This fundamental principle is a cornerstone of physics.

Question 13: Radiated heat waves will travel through space until they are absorbed by

an opaque object
air (Correct answer)
water
a transparent object

Correct answer: air

Radiated heat waves, such as infrared radiation, travel through the vacuum of space without needing a medium. Upon encountering matter, these waves can be absorbed, reflected, or transmitted. When traveling from space towards Earth, the atmosphere (composed of various gases, i.e., air) is the first significant medium encountered that absorbs a portion of this radiation, particularly infrared, contributing to atmospheric heating.

Question 14: What fire phenomenon can occur when fresh air is introduced into the fire area during the smoldering phase?

Pyrolysis
Flashover
Backdraft
None of the above (Correct answer)

Correct answer: None of the above

When fresh air (oxygen) is introduced into a fire area that is in the smoldering (decay) phase, characterized by high heat and a lack of oxygen, a phenomenon known as a backdraft can occur. This rapid influx of oxygen causes the superheated, unburnt gases to ignite explosively. Therefore, a backdraft is the specific fire phenomenon described.

Question 15: Flashover occurs during what phase of fire?

Incipient (growth)
Smoldering (decay)
Free-burning (fully developed)
All of the above (Correct answer)

Correct answer: All of the above

Flashover is a critical fire phenomenon that marks the transition from the growth stage to the fully developed stage of a compartment fire. It occurs when all combustible surfaces in a room are heated to their ignition temperature and ignite almost simultaneously due to radiant heat feedback. Therefore, flashover specifically occurs during the incipient (growth) phase, not during smoldering or fully developed stages.

Fire Science Basics Test

Wet wood is more difficult to ignite than dry wood.
Wood wll be very difficult to ignite then when the moisture rises content above