NFPA 921 – Guide for Fire and Explosion Investigations – Questions and Verified Answers – 2026

NFPA 921 Questions and
Answers


One Coulomb


Ans- 6.24 x 10(18) electrons




A BTU is equal to?


Ans- 1055 joules


1.055 kilojoules


252.15 calories




1 Calorie equals how many Joules?


Ans- 4.184 joules




How many Calories in a BTU?

,Ans- 252.15 calories




7 Step Scientific Method


Ans- Recognize the need (identify the problem)


Define the Problem


Collect Data


Analyze the Data


Develop Hypothesis (inductive reasoning)


Test the Hypothesis (deductive reasoning)


Select Final Hypothesis




Deductive reasoning


Ans- Test the hypothesis.




Two Levels of Certainty


Ans- Probable


Possible

,Probable Certainty


Ans- More likely true than not. The likelihood of the hypothesis being true is

greater than 50 percent.




Inductive reasoning


Ans- Develop a hypothesis.




Expectation Bias


Ans- Investigators reach a premature conclusion without having examined or

considered all of the relevant data.




Confirmation Bias


Ans- Investigator relies exclusively on data that supports the hypothesis and

fails to look for, ignores, or dismisses contradictory or nonsupporting data.




Possible Certainty

, Ans- The hypothesis can be demonstrated to be feasible but cannot be

declared probable. If two or more hypothesis are equally likely, then the level

of certainty must be "possible."




Flammable Range of Hydrogen


Ans- 71 percent (4% to 75%)




Thermal Conductivity (k)


Ans- A measure of the amount of heat that will flow across a unit area with a

temperature gradient of 1 degree per unit of length (W/m-K, Btu/hr-ft-F).




Heat Capacity (c)(specific heat)


Ans- A measure of the amount of heat necessary to raise the temperature of a

unit of mass 1 degree, under specific conditions (J/kg-K, Btu/lb-F).




Normal Ambient Temperature


Ans- 20 C, (68 F)