Ch. 3 Chemical Fires and Explosions

Question 1

Define explosion.

Answer 1

Sudden conversion of potential, chemical, or mechanical energy into kinetic energy resulting in the release of gases under pressure

Question 2

What are the 3 main types of explosions covered in class?

Answer 2

1) Chemical
2) Mechanical
3) Electrical

Question 3

Fire and explosions frequently accompany each other. With this knowledge, what is the fire investigator tasked with figuring out?

Answer 3

If the fire or the explosion came first

Question 4

What type of explosions are diffuse-phase and condensed-phase explosions?

Answer 4

Chemical

Question 5

Define diffuse-phase explosion.

Answer 5

Rapid combustion of fuel (gas, vapor, dust) premixed with air or oxygen and then ignited

Question 6

Define condensed-phase explosion.

Answer 6

Explosion not dependent on oxygen from the air.

Question 7

What 3 types of fuels can be found with diffuse-phase explosions?

Answer 7

Gases, vapor, and dust

Question 8

What is the most common type of fuel involved in a diffuse-phase explosion?

Answer 8

Natural gas

Question 9

Define deflagration.

Answer 9

Propagation of the combustion zone at a velocity less than the speed of sound in an unreacted medium

Question 10

How are deflagrations different than detonations?

Answer 10

Deflagrations are slower than the speed of sound while detonations are greater than the speed of sound

Question 11

Define backdraft.

Answer 11

Deflagration resulting from the sudden introduction of air into a confined space containing oxygen-deficient products of incomplete combustion

Question 12

Why do condensed-phase explosions not require oxygen from the air (HINT: 2 reasons)?

Answer 12

1) Fuel and oxidizer are mixed together
2) Monomolecular material itself is combustible

Question 13

How long does it take for a detonation to occur?

Answer 13

Microseconds

Question 14

How long does it take for a deflagration to occur?

Answer 14

Milliseconds to seconds

Question 15

Describe the relationship between the speed of an explosion and the force produced by it.

Answer 15

Greater explosion speed = greater explosive force

Question 16

A propellant is another term for a…

Answer 16

Low explosive

Question 17

Define low explosive.

Answer 17

Combustible materials that carry both fuel and necessary oxygen for their combustion

Question 18

What are two examples of low explosives?

Answer 18

Gun powder and flash powder

Question 19

Will a low explosive produce a deflagration or a detonation?

Answer 19

Deflagration

Question 20

Define high explosive (HINT: by the speed at which it moves).

Answer 20

Material capable of sustaining a reaction front that moves through material greater than or equal to the speed of sound

Question 21

Seeing that high explosives are capable of producing a supersonic reaction, do they function by detonation or deflagration?

Answer 21

Detonation

Question 22

What does IED stand for?

Answer 22

Improvised Explosive Device

Question 23

Name 2 types of high explosives.

Answer 23

Straight dynamite and TNT

Question 24

Define mechanical explosion.

Answer 24

Explosion where a container, vessel, or pipe bursts when internal gas or liquid pressures exceed the tensile strength of the container

Question 25

Do mechanical explosions involve chemical reactions?

Answer 25

No. They’re purely physical changes

Question 26

What does the acronym BLEVE stand for?

Answer 26

Boiling Liquid Expanding Vapor Explosion

Question 27

What is the cause of a BLEVE.

Answer 27

Mechanical failure resulting in the sudden release of contents

Question 28

Do the contents of a BLEVE have to be flammable to explode?

Answer 28

No

Question 29

The contents of a BLEVE may not have to be flammable, but they are well above their… (HINT: chemical property).

Answer 29

Boiling point

Question 30

Define electrical explosion.

Answer 30

Passage of high currents through air, insulating oil, or undersized conductors that cause very rapid heating and, in turn, an explosion