PHYSICAL CONSTANTS FOR INVESTIGATORS

by Tony Cafe

Reproduced from "Firepoint" magazine - Journal of Australian Fire Investigators.

At the fire scene the investigator essentially studies the effect of heat on the various materials which survived the fire. From this study, the investigator determines the nature of the fire, its progress from the area of origin and hopefully the cause of ignition. To successfully achieve this goal the investigator needs to refer to the scientific literature for the physical constants of the various materials found at the fire scene because the investigator's conclusions must be reached using a logical and scientific methodology.

The following tables should be of help to the fire investigator in understanding the cause and progress of the fire. The information has been extracted from various sources such as Kirk's Fire Investigation, Cooke & Ide's Principles of Fire Investigation, John N. Cardoulis' The Art and Science of Fire Investigation (1990) and the Fire Protection Handbook. All temperatures are in degrees Celsius and it is noted there exists some discrepancies in the literature of the various physical constants of materials and so the temperatures and constants should be treated as approximates.

INDEX OF TABLES

  1. TEMPERATURES AT FIRES

  2. PHYSICAL CONSTANTS OF MATERIALS

  3. TEMPERATURE INDICATORS

  4. FIRE CAUSES


1. TEMPERATURES AT FIRES

1.1 SOURCES OF IGNITION - GENERAL TEMPERATURES

Source

Temperature (Celsius)

Cigarettes - ventilated

400°-780°

Cigarettes - unventilated conditions

288°

Cigarettes - insulated and smoldering

510°-621°

Match

600°-800°

Candle flame

600°-1400°

Stove element

>550°

Fluorescent light

60°-80°

Incandescent light

100°-300°

Tungsten halogen light

600°-900°

Electrical arcing

to 3750°

Electrical spark

1316°

Lightning

30000°

Oxyacetylene

3300°

Industrial furnaces

1700°

Bunsen burner

1570°

1.2 COLOR TEMPERATURES OF HEAT

Dull red

500°-600°

Dark red

600°-800°

Bright red

800°-1000°

Yellow red

1000°-1200°

Bright yellow

1200°-1400°

White

1400°-1600°

1.3 TEMPERATURES DURING BUILDING FIRES

Hot gas layer

600°-1000°

Floor temperature

>180°

Glowing smoldering combustion

to 600°

Flashover

>600°

Glowing coals

to 1300°

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2. PHYSICAL CONSTANTS OF MATERIALS

2.1 SOLIDS

2.1.1 VARIOUS MATERIALS

Reactions to temperature exposure

Reaction

Temperature (Celsius)

Wood slowly chars*

120°-150°

Decayed wood ignites

150°

Ignition temp of various woods

190°-260°  

Paper yellows

150°

Paper ignites

218°-246°

Oil soaked lagging ignites

190°-220°

Leather ignites

212°

Hay ignites

172°

Coal ignites

400°-500°

* wood chars at a rate of approximately 30-50 mm/hour

2.1.2 PLASTICS

Melting points and ignition temperatures

Plastic

Melting Point
Range

Ignition Temperature

ABS

88°-125°

416°

Acrylics

91°-125°

560°

Cellulosics

49°-121°

475°-540°

Nylons

160°-275°

424°-532°

Polycarbonate

140°-150°

580°

Polyesters

220°-268°

432°-488°

Polyethylene ld

107°-124°

349°

Polyethylene hd

122°-137°

349°

Polypropylene

158°-168°

570°

Polystyrene

100°-120°

488°-496°

Polyurethanes

85°-121°

416°

PTFE

327°

530°

P.vinylideneclor

212°

454°

PVC

75°-110°

435°-557°

Wool

 

228°-230°

Cotton

 

250°

Rubber

 

260°-316°

2.1.3 METALS

Melting points and flame colours

(o) & (r) denote oxidizing and reducing conditions respectively

Metal

Melting Point

Flame Colour

Aluminium

660°

Colorless

Copper

1080°

Green (o) Red (r)

Lead

327°

Colorless

Tin

232°

Colorless

Bismuth

271°

Colorless

Zinc

419°

Colorless

Aluminium alloy

600°

Colorless

Antimony

630°

Colorless

Magnesium

651°

Colorless

Brass

900°-1000°

Green (o) Red (r)

Silver

961°

Colorless

Bronze

1000°

Green (o) Red (r)

Gold

1063°

 

Cast iron

1200°-1350°

Yellow-brown

Manganese

1260°

Violet (o)

Nickel

1450°

Brown-Red

Cobalt

1490°

Blue

Steel

1100°-1600°

Brown-Red

Platinum

1770°

 

Titanium

1670°

 

Chromium

1900°

Green

Tungsten

3410°

 

Solder 60/40

183°

 

Electric fuses

371°

 

Carbon

3730°

 

Pure iron

1535°

 

2.2 LIQUIDS

Boiling points, flash points, ignition temperature and heat of combustion

Liquid

Boiling Point

Flash Point

Ignition Temperature

Heat of Combustion
(kilocalories per gram)

Kerosene

175°-260°

38°-74°

229°

11

Gasoline

40°-190°

-43°

257°

11.5

Stove oil

190°-290°

     

Diesel

190°-340°

69°

399°

 

Fuel

200°-350°

     

Brake fluid

 

190°

   

Engine oil

 

150°-230°

260°-371°

 

Acetone

57°

-20°

465°

 

Benzene

80°

-11°

560°

10

Octane

126°

13°

220°

11.4

Pet ether

 

-18°

288°

 

Gum turpentine

 

37°

   

Spirit turpentine

135°-175°

35°

253°

 

Alcohol

78°

13°

365°

7.1

Ethylene glycol

 

111°

413°

 

Styrene

 

31°-37°

490°

 

White spirits

150°-200°

35°

232°

 

Asphalt

 

38°-121°

538°

 

Paint thinners

 

39°

245°

 

Paraffin wax

 

199°

   

* fire point is approximately 10°-50° above flash point

* cooking oil spontaneously combusts at 310°-360°

* temperature of flame from burning petrol is 471°-560°

2.3 GASES

Upper & lower flammable limits & ignition temperature

Gas

UFL %

LFL %

Ignition Temperature

Propane

9.6

2.15

466°

Butane

8.5

1.9

405°

Natural gas

15

4.7

482°-632°

Hydrogen

75

4

400°

Acetylene

3

65

335°

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3. TEMPERATURE INDICATORS

3.1 STEEL

Appearance

Temperature

Yellow

320°

Brown

350°

Purple

400°

Blue

450°

* loses 50% of its structural strength and sags at 550°

* melt point of steel 1100°-1650°

3.2 CONCRETE  AND  CEMENT

Appearance

Temperature

Reddish pink - reddish brown

300°

Gray

300°-1000°

Buff

>1000°

Sinters and yellowish

>1200°

* sand and sandstone becomes friable at 573°

* wall masonry collapses at 760°

3.3 GLASS

Effect

Soda

Borosilicate

Very slight distortion

700°

750°

Slight distortion

750°

800°

Considerable distortion

800°

850°

Medium fluid flow

850°

900°

Liquid flow

900°

950°

* glass thermally cracks at 90°-120°

3.4 MINERAL WOOL INSULATION

Effect

Temperature

Resin chars & slowly blackens

288°

Resin chars quickly

400°

Fibers becomes light gray

482°

Fibers fuse

593°

Fibers melt

649°

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4. FIRE CAUSES

4.1 ACCIDENTAL  FIRE  CAUSES

  • Defective or left on heating or cooking equipment 
  • Defective chimney or flue 
  • Hot ashes or coals
  • Combustibles near heaters
  • Smoking or matches
  • Electrical
  • Rubbish fires
  • Chimney or bushfire sparks on roof
  • Welding and cutting
  • Friction sparks from clashing metals
  • Overheating of machinery
  • Candles
  • Poor storage of flammable liquids
  • Lightning
  • Children and matches
  • Spontaneous ignition
  • Gas and gas appliances

4.2 ARSON  INDICATORS

  • Presence of flammable liquids
  • Multiple points of origin
  • Use of trailers, timing devices
  • Presence of explosion
  • Sign of forced entry
  • Sign of contents removed before the fire or replaced with inferior goods 
  • Signs of tampering with gas or electric appliances or sprinklers
  • Signs of artificial drafts eg holes in walls
  • Rapid onset of fire, higher than normal temperatures closet fires
  • Other crime committed

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