F80 Fire Behavior and Combustion Principles 5

Question 1

Which type of flame is produced when fuel and oxygen are mixed before reaching the combustion zone?

Accepted Answer

Premixed flame

Answer

A premixed flame occurs when fuel and oxidizer are combined prior to ignition, as in a Bunsen burner, producing a hotter and more complete combustion than a diffusion flame.

Question 2

What is the upper flammable limit (UFL) of a gas mixture?

Accepted Answer

The concentration above which there is too much fuel and too little oxygen to ignite

Answer

The upper flammable limit is the maximum fuel concentration in air above which the mixture is too rich in fuel (oxygen-deficient) to support ignition.

Question 3

A fire doubles in size every minute under certain conditions. This exponential growth phase is best described as:

Accepted Answer

Incipient (growth) phase

Answer

During the incipient or growth phase, a fire can grow exponentially as it gains access to additional fuel and oxygen before being limited by compartment conditions.

Question 4

Which type of heat transfer does NOT require a medium (can occur through a vacuum)?

Accepted Answer

Radiation

Answer

Radiation transfers heat via electromagnetic waves and requires no physical medium, allowing it to travel through a vacuum unlike conduction or convection.

Question 5

When comparing Class A and Class B fires, which statement about extinguishment is correct?

Accepted Answer

Class A fires benefit from water's cooling and soaking action on deep-seated embers

Answer

Water is effective on Class A (ordinary combustible) fires because it cools the fuel below ignition temperature and penetrates to extinguish deep-seated embers.

F80 Practice Test

F80 Practice Test

F80 Fire Behavior and Combustion Principles 5