Fire, Arson and Explosives Questions and Answers

Q: ANFO commercial explosive consists of :

ANFO is ammonium nitrate + fuel oil.The name is an acronym: Ammonium Nitrate and Fuel Oil. Prilled ammonium nitrate (the oxidiser) is mixed with about 6 percent fuel oil (the fuel), giving a cheap, safe-to-handle blasting agent used widely in mining and quarrying. It needs a booster charge to detonate. Its ingredients are easy to obtain, so it has also been used in large vehicle bombs, which is why it matters in forensic explosives work.Sodium, potassium and calcium nitrate are other oxidisers (potassium nitrate is the oxidiser in black powder), but none is the AN in ANFO.

Q: Coal oil is also known as :

Coal oil is another name for kerosene.Kerosene was first made in the nineteenth century by distilling coal and oil shale, which is why it was called coal oil; the name stayed in use after it came to be distilled from petroleum. It is the fraction boiling at roughly 150 to 275°C, used as lamp and stove fuel and as jet fuel. In fire investigation it is a common accelerant identified by its pattern of hydrocarbons in gas chromatography.Petrol (gasoline) is a lighter fraction, and diesel and gas oil are heavier fractions. None of them is called coal oil.

Q: A petroleum product having a lower carbon limit of C1 and an upper carbon limit of C4 is known as :

A product spanning C1 to C4 is refinery gas.Refinery gas is the lightest fraction from crude oil distillation, made up of methane, ethane, propane and butane (one to four carbon atoms). Propane and butane are also liquefied as LPG.Gasoline contains roughly C4/C5 to C12 hydrocarbons, aviation turbine fuel (kerosene) about C8 to C16, and lubricating oils much heavier molecules of about C20 and above.

Q: Corrosiveness of gasoline is caused due to the presence of :

The corrosiveness of gasoline is caused by sulfur.Sulfur compounds left from crude oil, such as hydrogen sulphide, mercaptans and free sulfur, attack metals, especially copper and its alloys in fuel systems. The copper strip corrosion test measures this, and fuel standards limit sulfur content partly for this reason.Water can cause rusting in tanks but is not a constituent responsible for the corrosiveness of the fuel itself, chloride is not a normal gasoline component, and lead (as tetraethyl lead) was an anti-knock additive.

Q: Double base smokeless powder contains :

Double base smokeless powder contains nitrocellulose and nitroglycerine.Single base powder is nitrocellulose alone. Double base powder adds nitroglycerine, which raises the energy, and triple base powder adds nitroguanidine as well. These smokeless propellants replaced black powder in modern ammunition.Potassium chlorate and arsenic or antimony sulphides are ingredients of primer and pyrotechnic mixtures, not of smokeless propellant, and potassium chloride is not an explosive ingredient.

Q: Which of the following is the unit for Heat Release Rate (HRR) ?

Heat Release Rate is measured in kilowatts.HRR is the rate at which a fire releases energy, so it is energy per unit time: joules per second, that is watts. Fires are described in kilowatts or megawatts; a burning upholstered chair may peak at around 1-2 MW. HRR is the single most important quantity in fire investigation and modelling, because it governs flame height, temperature and how quickly a room reaches flashover.A kilojoule is a total quantity of energy, not a rate. Kilowatt per kelvin and kilojoule per kelvin are units of heat transfer coefficient and heat capacity, not of heat release.

Q: Which of the following refers to shattering power of an explosive ?

The shattering power of an explosive is its brisance (spelt 'Brisonce' in the paper).Brisance comes from the French briser, to break. It depends mainly on the detonation velocity and density of the explosive, and it is measured by tests such as the sand crush and plate dent tests. High explosives such as RDX have high brisance.Detonation is the process itself, a supersonic reaction front, not a measure of shattering effect. Deflagration is subsonic burning, as in propellants, and flame speed is a property of burning, not of shattering.

Q: Cordite contains :

Cordite contains nitroglycerine 58%, nitrocellulose 37% and mineral jelly 5%.That is the composition of the original Cordite Mark I, the British double-base smokeless propellant used in the .303 cartridge. Nitroglycerine and nitrocellulose are the energetic ingredients, and mineral jelly (petroleum jelly) acts as a stabiliser and reduces barrel erosion. The later Cordite MD reduced the nitroglycerine to 30% and raised the nitrocellulose to 65%.Swapping the two main percentages gives a mixture that was not cordite, and the two-component options leave out an ingredient.

Q: The most widely measured smoke property is :

The most widely measured smoke property is the light extinction coefficient.Smoke reduces visibility by absorbing and scattering light. Passing a light beam through the smoke and measuring how much is lost (by the Beer-Lambert relation) gives the extinction coefficient, which is used to calculate visibility through smoke and to compare how smoky different materials are in fire tests.A Henry coefficient describes how a gas dissolves in a liquid, and 'Burgis' and 'Bonger' coefficients are not smoke properties at all.

Q: Which of the following is having the highest detonation velocity ?

The highest detonation velocity belongs to HMX.Approximate detonation velocities at full density are:HMX (octogen): about 9,100 m/sRDX: about 8,750 m/sPETN: about 8,400 m/sTNT: about 6,900 m/sHMX is the denser eight-membered ring relative of RDX, and its higher density and energy give it the greatest velocity of the four, which is why it is used in high-performance charges. TNT is the slowest of the group.

ANFO commercial explosive consists of :

A.Ammonium nitrate + fuel oil
B.Sodium nitrate + fuel oil
C.Potassium nitrate + fuel oil
D.Calcium nitrate + fuel oil

Exam Year(s)

MH SET - 2018, SET Exam - 2018,

Answer: A

ANFO is ammonium nitrate + fuel oil.

The name is an acronym: Ammonium Nitrate and Fuel Oil. Prilled ammonium nitrate (the oxidiser) is mixed with about 6 percent fuel oil (the fuel), giving a cheap, safe-to-handle blasting agent used widely in mining and quarrying. It needs a booster charge to detonate. Its ingredients are easy to obtain, so it has also been used in large vehicle bombs, which is why it matters in forensic explosives work.

Sodium, potassium and calcium nitrate are other oxidisers (potassium nitrate is the oxidiser in black powder), but none is the AN in ANFO.

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Coal oil is also known as :

A.Petrol
B.Diesel
C.Gas oil
D.Kerosene

Exam Year(s)

MH SET - 2018, SET Exam - 2018,

Answer: D

Coal oil is another name for kerosene.

Kerosene was first made in the nineteenth century by distilling coal and oil shale, which is why it was called coal oil; the name stayed in use after it came to be distilled from petroleum. It is the fraction boiling at roughly 150 to 275°C, used as lamp and stove fuel and as jet fuel. In fire investigation it is a common accelerant identified by its pattern of hydrocarbons in gas chromatography.

Petrol (gasoline) is a lighter fraction, and diesel and gas oil are heavier fractions. None of them is called coal oil.

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A petroleum product having a lower carbon limit of C₁ and an upper carbon limit of C₄ is known as :

A.Aviation fuel
B.Gasoline
C.Lubricating oil
D.Refinery gas

Exam Year(s)

MH SET - 2018, SET Exam - 2018,

Answer: D

A product spanning C₁ to C₄ is refinery gas.

Refinery gas is the lightest fraction from crude oil distillation, made up of methane, ethane, propane and butane (one to four carbon atoms). Propane and butane are also liquefied as LPG.

Gasoline contains roughly C₄/C₅ to C₁₂ hydrocarbons, aviation turbine fuel (kerosene) about C₈ to C₁₆, and lubricating oils much heavier molecules of about C₂₀ and above.

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Corrosiveness of gasoline is caused due to the presence of :

A.Sulfur
B.Water
C.Chloride
D.Lead

Exam Year(s)

MH SET - 2018, SET Exam - 2018,

Answer: A

The corrosiveness of gasoline is caused by sulfur.

Sulfur compounds left from crude oil, such as hydrogen sulphide, mercaptans and free sulfur, attack metals, especially copper and its alloys in fuel systems. The copper strip corrosion test measures this, and fuel standards limit sulfur content partly for this reason.

Water can cause rusting in tanks but is not a constituent responsible for the corrosiveness of the fuel itself, chloride is not a normal gasoline component, and lead (as tetraethyl lead) was an anti-knock additive.

Discuss in Forum

Double base smokeless powder contains :

A.Potassium chlorate and arsenic sulphide
B.Nitrocellulose and nitroglycerine
C.Nitrocellulose and potassium chlorate
D.Nitroglycerine and potassium chloride

Exam Year(s)

MH SET - 2018, SET Exam - 2018,

Answer: B

Double base smokeless powder contains nitrocellulose and nitroglycerine.

Single base powder is nitrocellulose alone. Double base powder adds nitroglycerine, which raises the energy, and triple base powder adds nitroguanidine as well. These smokeless propellants replaced black powder in modern ammunition.

Potassium chlorate and arsenic or antimony sulphides are ingredients of primer and pyrotechnic mixtures, not of smokeless propellant, and potassium chloride is not an explosive ingredient.

Discuss in Forum

Which of the following is the unit for Heat Release Rate (HRR) ?

A.Kilowatt
B.Kilo joule
C.Kilowatt per kelvin
D.Kilo joule per kelvin

Exam Year(s)

MH SET - 2019, SET Exam - 2019,

Answer: A

Heat Release Rate is measured in kilowatts.

HRR is the rate at which a fire releases energy, so it is energy per unit time: joules per second, that is watts. Fires are described in kilowatts or megawatts; a burning upholstered chair may peak at around 1-2 MW. HRR is the single most important quantity in fire investigation and modelling, because it governs flame height, temperature and how quickly a room reaches flashover.

A kilojoule is a total quantity of energy, not a rate. Kilowatt per kelvin and kilojoule per kelvin are units of heat transfer coefficient and heat capacity, not of heat release.

Discuss in Forum

Which of the following refers to shattering power of an explosive ?

A.Flame speed
B.Deflagration
C.Detonation
D.Brisonce

Exam Year(s)

MH SET - 2019, SET Exam - 2019,

Answer: D

The shattering power of an explosive is its brisance (spelt 'Brisonce' in the paper).

Brisance comes from the French briser, to break. It depends mainly on the detonation velocity and density of the explosive, and it is measured by tests such as the sand crush and plate dent tests. High explosives such as RDX have high brisance.

Detonation is the process itself, a supersonic reaction front, not a measure of shattering effect. Deflagration is subsonic burning, as in propellants, and flame speed is a property of burning, not of shattering.

Discuss in Forum

Cordite contains :

A.Nitroglycerine (58%) nitrocellulose (37%) and mineral jelly (5%)
B.Nitroglycerine (37%) nitrocellulose (58%) and mineral jelly (5%)
C.Nitroglyecrine (58%) and Nitrocellulose (42%)
D.Nitrocellulose (58%) and mineral jelly (42%)

Exam Year(s)

MH SET - 2019, SET Exam - 2019,

Answer: A

Cordite contains nitroglycerine 58%, nitrocellulose 37% and mineral jelly 5%.

That is the composition of the original Cordite Mark I, the British double-base smokeless propellant used in the .303 cartridge. Nitroglycerine and nitrocellulose are the energetic ingredients, and mineral jelly (petroleum jelly) acts as a stabiliser and reduces barrel erosion. The later Cordite MD reduced the nitroglycerine to 30% and raised the nitrocellulose to 65%.

Swapping the two main percentages gives a mixture that was not cordite, and the two-component options leave out an ingredient.

Discuss in Forum

The most widely measured smoke property is :

A.Light extinction coefficient
B.Burgis coefficient
C.Henry coefficient
D.Bonger coefficient

Exam Year(s)

MH SET - 2019, SET Exam - 2019,

Answer: A

The most widely measured smoke property is the light extinction coefficient.

Smoke reduces visibility by absorbing and scattering light. Passing a light beam through the smoke and measuring how much is lost (by the Beer-Lambert relation) gives the extinction coefficient, which is used to calculate visibility through smoke and to compare how smoky different materials are in fire tests.

A Henry coefficient describes how a gas dissolves in a liquid, and 'Burgis' and 'Bonger' coefficients are not smoke properties at all.

Discuss in Forum

10.

Which of the following is having the highest detonation velocity ?

A.HMX
B.PETN
C.TNT
D.RDX

Exam Year(s)

MH SET - 2019, MH SET - 2021, SET Exam - 2019, SET Exam - 2021,

Answer: A

The highest detonation velocity belongs to HMX.

Approximate detonation velocities at full density are:

HMX (octogen): about 9,100 m/s
RDX: about 8,750 m/s
PETN: about 8,400 m/s
TNT: about 6,900 m/s

HMX is the denser eight-membered ring relative of RDX, and its higher density and energy give it the greatest velocity of the four, which is why it is used in high-performance charges. TNT is the slowest of the group.

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