Chapter 3 Chemical Fires and Explosions Flashcards
What are the four categories of explosions?
Chemical (including explosible dusts), mechanical, electrical and nuclear
What are the two types of explosive mixtures and what is the difference?
Diffusive (chemical mixes with air)and Condensed-phase (explosive oxidizes within itself)
What impacts diffuse-phase explosions
Type of fuel, concentration, ignition mechanism and degree of confinement
If LP gas is a possible cause of a chemical explosion, what must be investigated?
Recent repair work, appliance installations, or any other sources of furtive gas
Which type of fuel gas can detonate under some conditions
Acetylene
With the exception of natural gas, the vapor densities of most flammable gases in comparison to air are?
Heavier than air
The propagation of vapors from a spill or flammable liquid are affected by?
Type of fuel, present of draft conditions or other air movement.
What is necessary for a pressure effect to be produced in a deflagration
confinement of reaction in a rigid container or structure
What two factors extend the explosive range?
Heat and pressurization
UCVE
Unconfined vapor cloud explosion
What are the resulting pressures achieved from a backdraft?
.5 to 1.5psi
What is the major difference between gas/air deflagrations and dust explosions?
Dust on surfaces can be agitated during the initial phase and will propagate the deflagration much longer
In order for an ignition source to ignite a flammable mixture what must be present
The fuel mixture must be present in combustible concentrations in the immediate area of the heat source.
What do condensed-phase explosions involve
Liquid or gel explosives in which the fuel and oxidized are mechanically mixed or is able to undergo extremely rapid conversion
What do most high explosives require?
An initiating mechanical shock that triggers a cascade effect of reactions throughout the reaction volume
Brisance
Shattering power
What compounds form the most common types of explosive chemicals
Nitrogen compounds
What is one of the most widely used improvised explosive materials
TATP (Tri-acetone, tri-peroxide) made with hair polish remover, hair bleach, and batteries
Contents of hobby fuse
pyrotechnic powder wrapped in windings of fine string and coated with a nitrocellulose lacquer
Contents of safety fuse
Finely ground black powder supported by wrappings of string, tar and plastic
Contents of igniter cord
Perchlorate-based incendiary filler with a multiple spiral wrap of fine, nickel-chrome iron wire
Elements of a firing train
initial heat source, fuse, blasting cap, booster, and main charge
Mechanical explosion
container or vessel that bursts when the internal gas or liquid pressures exceed the tensile strength of the container
