Fire, Arson and Explosives Questions and Answers

Q: The knock rating of a gasoline is expressed also by its :

The knock rating of gasoline is expressed by its octane number.Knocking is the premature, uncontrolled ignition of the fuel-air mixture in a spark-ignition engine. The octane number measures a fuel's resistance to knocking by comparing it with a mixture of iso-octane (2,2,4-trimethylpentane, rated 100) and n-heptane (rated 0). A fuel with octane number 91 knocks like a mixture of 91 per cent iso-octane and 9 per cent heptane.Heptane is one of the reference fuels, not the scale. There is no propane number, and the aniline point is used to characterise the aromatic content of oils and diesel, not knock.

Q: Which of the following is not a constituent of black powder ?

The substance not in black powder is ammonium nitrate.Black powder (gunpowder), the oldest propellant and low explosive, is a mixture of about 75 per cent potassium nitrate (saltpetre) as the oxidiser, 15 per cent charcoal and 10 per cent sulphur as fuels. It is still used in fireworks, fuses and muzzle-loading firearms, and its residues (nitrate, sulphate, sulphide and charcoal) are examined in explosion cases.Ammonium nitrate is the oxidiser in ANFO and many commercial explosives and improvised devices, but it is not a component of black powder.

Q: Which of the following military explosives is having the lowest detonation velocity ?

The explosive with the lowest detonation velocity is Amatol.Amatol is a mixture of TNT and ammonium nitrate. The ammonium nitrate lowers its brisance, and its detonation velocity is roughly 5,000 to 6,500 m/s depending on the proportions.The others are faster. Composition C-4, an RDX-based plastic explosive, detonates at about 8,000 m/s; Torpex (RDX, TNT and aluminium) and Tetryl both at about 7,500 m/s. Amatol was valued in the World Wars because ammonium nitrate was cheap, not because it was powerful.

Q: "V" pattern in a fire scene indicates :

A 'V' pattern in a fire scene indicates the point of origin.Fire spreads upward and outward from where it starts, so on a wall it leaves a burn pattern shaped like a V, whose low point is near the origin of the fire. Investigators trace these patterns back to locate where it began.The pattern's shape can say something about the fire's intensity and ventilation, but it does not by itself show the type of fire, the type of fuel or the full extent of the damage; its main use is to locate the origin.

Q: MMAN, EGM, HTMAN and MEAN are the examples of :

MMAN, EGM, HTMAN and MEAN are sensitizers.Water gel and slurry explosives based on ammonium nitrate need sensitizers to make them detonate reliably. Compounds such as monomethylamine nitrate (MMAN), ethylene glycol mononitrate and monoethanolamine nitrate (MEAN) are used for this purpose.They are not detonators (devices that start the detonation), oxidizers (the ammonium nitrate itself plays that role) or stabilizers (which slow decomposition in propellants).

Q: ASTM D-96, ASTM D-207, ASTM D-1086, ASTM D-1298 are the test to measure the different properties of :

These ASTM tests measure properties of petroleum products.ASTM's D series includes the standard methods for petroleum: D-1298, for example, is the hydrometer method for density and API gravity of crude oil and liquid petroleum products, and D-96 determines water and sediment in crude oil by centrifuge. Forensic laboratories use such methods when examining fuels, adulteration and fire debris.Alcoholic beverages, organic acids and GC columns are not what this group of standards covers.

Q: Match the common additives given in List-I with that of their action in List-II used in petro product :List-IList-II(a) Aromatic amino and hindered phenols(i) Demulsifiers(b) Carboxylic acid and carboxylates(ii) Oxidation inhibitors(c) Polyglycol derivatives(iii) Anti-icing additive(d) Surfactants(iv) Corrosion inhibitorsCodes :

The correct matching is a-(ii), b-(iv), c-(i), d-(iii).Aromatic amines and hindered phenols are antioxidants, so they are oxidation inhibitors in fuels and lubricants. Carboxylic acids and their salts form protective films on metal, acting as corrosion inhibitors. Polyglycol derivatives break water-oil emulsions, acting as demulsifiers. Surface-active agents keep ice from forming and sticking in fuel systems, serving as anti-icing additives.Once a-(ii) and b-(iv) are fixed, only the first code fits; the others pair the antioxidants or the acids with the wrong function.

Q: Cyclotol is the combination of :

Cyclotol is a mixture of RDX and TNT.Cyclotol is a castable military explosive of RDX (cyclotrimethylenetrinitramine, called cyclonite, hence the name) and TNT, commonly in proportions such as 60:40, 70:30 or 75:25. The molten TNT carries the more powerful RDX so that it can be cast into shells and warheads.PETN with TNT is pentolite, used in boosters. PETN with RDX is not cyclotol, and black powder with nitrocellulose is a propellant mixture, not a high explosive.

Q: The phenomenon that occurs when all the combustible fuels simul-taneously ignites, engulfing the entire structure in flames is known as :

The phenomenon is flashover.In a compartment fire, hot gases collect under the ceiling and radiate heat down onto the room's contents. When the surfaces of all the combustible materials reach their ignition temperature together, they ignite almost at once and the whole room is engulfed in flames. This transition from a growing fire to a fully developed one is flashover.A backdraft is an explosive burning that occurs when air is suddenly let into an oxygen-starved fire. Pyrolysis is the chemical decomposition of fuel by heat that produces flammable gases, and detonation is a supersonic explosive reaction.

21.

The knock rating of a gasoline is expressed also by its :

A.Heptane number
B.Octane number
C.Propane number
D.Aniline gravity

Exam Year(s)

MH SET - 2021, SET Exam - 2021,

Answer: B

The knock rating of gasoline is expressed by its octane number.

Knocking is the premature, uncontrolled ignition of the fuel-air mixture in a spark-ignition engine. The octane number measures a fuel's resistance to knocking by comparing it with a mixture of iso-octane (2,2,4-trimethylpentane, rated 100) and n-heptane (rated 0). A fuel with octane number 91 knocks like a mixture of 91 per cent iso-octane and 9 per cent heptane.

Heptane is one of the reference fuels, not the scale. There is no propane number, and the aniline point is used to characterise the aromatic content of oils and diesel, not knock.

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22.

Which of the following is not a constituent of black powder ?

A.Potassium nitrate
B.Charcoal
C.Ammonium nitrate
D.Sulphur

Exam Year(s)

MH SET - 2021, SET Exam - 2021,

Answer: C

The substance not in black powder is ammonium nitrate.

Black powder (gunpowder), the oldest propellant and low explosive, is a mixture of about 75 per cent potassium nitrate (saltpetre) as the oxidiser, 15 per cent charcoal and 10 per cent sulphur as fuels. It is still used in fireworks, fuses and muzzle-loading firearms, and its residues (nitrate, sulphate, sulphide and charcoal) are examined in explosion cases.

Ammonium nitrate is the oxidiser in ANFO and many commercial explosives and improvised devices, but it is not a component of black powder.

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23.

Which of the following military explosives is having the lowest detonation velocity ?

A.Composition C-4
B.Amatol
C.Torpex
D.Tetryl

Exam Year(s)

MH SET - 2023, SET Exam - 2023,

Answer: B

The explosive with the lowest detonation velocity is Amatol.

Amatol is a mixture of TNT and ammonium nitrate. The ammonium nitrate lowers its brisance, and its detonation velocity is roughly 5,000 to 6,500 m/s depending on the proportions.

The others are faster. Composition C-4, an RDX-based plastic explosive, detonates at about 8,000 m/s; Torpex (RDX, TNT and aluminium) and Tetryl both at about 7,500 m/s. Amatol was valued in the World Wars because ammonium nitrate was cheap, not because it was powerful.

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24.

The conventional black powder consists of potassium nitrate, charcoal and sulphur in a proportion of :

A.70 : 10 : 20
B.85 : 10 : 5
C.75 : 15 : 10
D.75 : 10 : 15

Exam Year(s)

MH SET - 2023, SET Exam - 2023,

Answer: C

Conventional black powder is potassium nitrate, charcoal and sulphur in the proportion 75 : 15 : 10.

This is the standard gunpowder formula: about 75 per cent potassium nitrate (the oxidiser), 15 per cent charcoal (the fuel) and 10 per cent sulphur, which lowers the ignition temperature and speeds burning.

75 : 10 : 15 swaps the charcoal and sulphur, and 70 : 10 : 20 and 85 : 10 : 5 are not the conventional proportions. A useful check is that saltpetre is always the largest part and charcoal the second.

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25.

"V" pattern in a fire scene indicates :

A.Type of fire
B.Point of origin
C.Type of fuel used
D.Extent of fire

Exam Year(s)

MH SET - 2023, SET Exam - 2023,

Answer: B

A 'V' pattern in a fire scene indicates the point of origin.

Fire spreads upward and outward from where it starts, so on a wall it leaves a burn pattern shaped like a V, whose low point is near the origin of the fire. Investigators trace these patterns back to locate where it began.

The pattern's shape can say something about the fire's intensity and ventilation, but it does not by itself show the type of fire, the type of fuel or the full extent of the damage; its main use is to locate the origin.

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26.

MMAN, EGM, HTMAN and MEAN are the examples of :

A.Detonators
B.Oxidizers
C.Sensitizers
D.Stabilizers

Exam Year(s)

MH SET - 2023, SET Exam - 2023,

Answer: C

MMAN, EGM, HTMAN and MEAN are sensitizers.

Water gel and slurry explosives based on ammonium nitrate need sensitizers to make them detonate reliably. Compounds such as monomethylamine nitrate (MMAN), ethylene glycol mononitrate and monoethanolamine nitrate (MEAN) are used for this purpose.

They are not detonators (devices that start the detonation), oxidizers (the ammonium nitrate itself plays that role) or stabilizers (which slow decomposition in propellants).

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27.

ASTM D-96, ASTM D-207, ASTM D-1086, ASTM D-1298 are the test to measure the different properties of :

A.Petroleum Products
B.Alcoholic Beverages
C.Organic Acids
D.Columns used in GC

Exam Year(s)

MH SET - 2023, SET Exam - 2023,

Answer: A

These ASTM tests measure properties of petroleum products.

ASTM's D series includes the standard methods for petroleum: D-1298, for example, is the hydrometer method for density and API gravity of crude oil and liquid petroleum products, and D-96 determines water and sediment in crude oil by centrifuge. Forensic laboratories use such methods when examining fuels, adulteration and fire debris.

Alcoholic beverages, organic acids and GC columns are not what this group of standards covers.

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28.

Match the common additives given in List-I with that of their action in List-II used in petro product :

List-I	List-II
(a) Aromatic amino and hindered phenols	(i) Demulsifiers
(b) Carboxylic acid and carboxylates	(ii) Oxidation inhibitors
(c) Polyglycol derivatives	(iii) Anti-icing additive
(d) Surfactants	(iv) Corrosion inhibitors

Codes :

A.a-(ii), b-(iv), c-(i), d-(iii)
B.a-(ii), b-(i), c-(iv), d-(iii)
C.a-(iii), b-(iv), c-(i), d-(ii)
D.a-(iii), b-(i), c-(iv), d-(ii)

Exam Year(s)

MH SET - 2023, SET Exam - 2023,

Answer: A

The correct matching is a-(ii), b-(iv), c-(i), d-(iii).

Aromatic amines and hindered phenols are antioxidants, so they are oxidation inhibitors in fuels and lubricants. Carboxylic acids and their salts form protective films on metal, acting as corrosion inhibitors. Polyglycol derivatives break water-oil emulsions, acting as demulsifiers. Surface-active agents keep ice from forming and sticking in fuel systems, serving as anti-icing additives.

Once a-(ii) and b-(iv) are fixed, only the first code fits; the others pair the antioxidants or the acids with the wrong function.

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29.

Cyclotol is the combination of :

A.PETN+TNT
B.RDX+TNT
C.PETN+RDX
D.Black powder+Nitrocellulose

Exam Year(s)

MH SET - 2024, SET Exam - 2024,

Answer: B

Cyclotol is a mixture of RDX and TNT.

Cyclotol is a castable military explosive of RDX (cyclotrimethylenetrinitramine, called cyclonite, hence the name) and TNT, commonly in proportions such as 60:40, 70:30 or 75:25. The molten TNT carries the more powerful RDX so that it can be cast into shells and warheads.

PETN with TNT is pentolite, used in boosters. PETN with RDX is not cyclotol, and black powder with nitrocellulose is a propellant mixture, not a high explosive.

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30.

The phenomenon that occurs when all the combustible fuels simul-taneously ignites, engulfing the entire structure in flames is known as :

A.Backdraft fire
B.Pyrolysis
C.Flashover
D.Detonation

Exam Year(s)

MH SET - 2024, SET Exam - 2024,

Answer: C

The phenomenon is flashover.

In a compartment fire, hot gases collect under the ceiling and radiate heat down onto the room's contents. When the surfaces of all the combustible materials reach their ignition temperature together, they ignite almost at once and the whole room is engulfed in flames. This transition from a growing fire to a fully developed one is flashover.

A backdraft is an explosive burning that occurs when air is suddenly let into an oxygen-starved fire. Pyrolysis is the chemical decomposition of fuel by heat that produces flammable gases, and detonation is a supersonic explosive reaction.

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