Fire Scene vs Gasoline

Gasoline Characteristics

A gallon of gasoline has the kinetic energy of 80 million foot pounds (average) or 123,000 Btu. One gallon = 33 kilowatt hours. This is the equivalent of 33 space heaters in the Meadows’ north hall and stairway running on high for an hour. How hot would that be? Do you think there would be any paint, plastic or carpet left unblistered or unburned? If a gallon of gasoline had been spread and ignited with a cigarette lighter, the ignition and explosion would have blown out all the windows and doors of that hallway. It would have seriously burned, ejected (propelled), and likely killed the arsonist, and even the individuals in apartments attached to that hallway would have been seriously injured or killed. However, the individuals living in that hallway walked out uninjured and unharmed. The fire would not have burned out before the fire department arrived, had gasoline been used.

Meadows North Wing Structural Dimensions

The fire took place in the north, upper hallway and adjacent stairwell.

North Hallway

5 ft wide, 10 ft high, 56 ft long (Note the height includes the static ceiling, not just the drop-ceiling at 7.5 ft. No ceiling tiles or panels were lifted or displaced as a result of the fire.)

Total Surface Area: ~1800 sq. ft | Volume: ~2800 cu. ft

North Stairwell

The north stairwell is a folded stairway with a common ceiling that is tapered at an angle approximately following the upper half of the folded stairway, while the lower half continues downward underneath it. Underneath the upper flight of stairs is a small alcove.

Total Stairwell Surface Area: ~900 sq. ft | Volume: ~1400 cu. ft

Expected Gasoline Energy Expenditure

Investigators of the Meadows Carpet Fire implied that either about 1 cup or 1 gallon of gasoline was distributed through the hallway and stairwell.

A foot-pound (ft-lb) is the amount of energy or force required to lift one pound one foot. It is not dependent on time.

Our calculations assume that all the energy was converted into mechanical physical force (foot-pounds) of thrust and that portions of it were not lost as heat. Reflected energies from the rigid, static surfaces would add to, and find relief at, the weakest points of the structure (i.e. glass windows and doors).

On this page we use the average force values for different blends of gasoline. Given that a gallon of gasoline has the kinetic energy of about 80 million foot-pounds of force (the average value for different blends of gasoline):

  • 1 gal gasoline: 80,000,000 ft-lb, enough force to lift 80,000,000 pounds one foot, or lift one pound 80,000,000 feet.
  • 1 cup gasoline = 1/16 gal gasoline: 5,000,000 ft-lb, enough force to lift 5,000,000 pounds one foot, or lift one pound 5,000,000 feet.

Scenario: 1/2 gallon gasoline

If 1/2 gal of gasoline is distributed in the hallway and the remaining 1/2 gal is used in the stairwell.

1/2 gal gasoline provides 40,000,000 ft-lb of force.

Hallway: 40,000,000 ft-lb / 1800 sq. ft surface area in hallway = 22000 lb / sq. ft, or 11 tons force on each square foot in hallway!

Hallway glass window area: 4.5 ft x 6 ft = 27 sq. ft. The total force against the hallway window is 22000 lb * 27 sq. ft = 594000 lb (or 297 tons) against the window! Each of the 21-sq. ft doors within that hallway * 22000 lb per sq. ft, would experience 462000 lb (or 231 tons) of force.

Stairwell: 40,000,000 ft-lb / 900 sq. ft surface area in stairwell = 44,000 lb / sq. ft, or 22 tons force on each square foot in stairwell!

Stairwell glass window area: 7 ft x 3 ft = 21 sq. ft. The total force against the stairwell window is 44000 lb * 21 sq. ft = 924000 lb (or 460 tons) against the window! The stairwell doors are also 21 sq. ft and would also experience the same force.

Scenario: 1/2 cup gasoline

Now, if 1/2 cup(!) of gasoline is distributed in the hallway and the remaining 1/2 cup is used in the stairwell.

1/2 cup gasoline provides 2,500,000 ft-lb of force.

Hallway: 2,500,000 ft-lb / 1800 sq. ft surface area in hallway = 1400 lb / sq. ft, or 0.7 tons force on each square foot in hallway!

Hallway glass window area: 4.5 ft x 6 ft = 27 sq. ft. The total force against the hallway window is 1400 lb * 27 sq. ft = 38000 lb (or 19 tons) of force against the window! Each of the 21-sq. ft doors within that hallway * 1400 lb per sq. ft, would experience 29000 lb (or 14.7 tons) of force.

Stairwell: 2,500,000 ft-lb / 900 sq. ft surface area in stairwell = 2800 lb / sq. ft, or 1.4 tons force on each square foot in stairwell!

Stairwell glass window area: 7 ft x 3 ft = 21 sq. ft. The total force against the stairwell window is 2800 lb * 21 sq. ft = 59000 lb (or 29.5 tons) against the window! The stairwell doors would experience the same force.

Tenths of a half cup of gasoline

Again, if that 1/2 cup of gasoline was distributed in the Meadows hallway, and another 1/2 cup distributed in the attached stairwell. But this time, let us presume that only 1/10th of either half cup ignited and combusted in the initial milliseconds of ignition, which would cause an explosion.

Hallway: If only a tenth of the total energy of the above half cup of gasoline was expended in the initial hallway explosion, would the window stay in place? The hallway glass window would experience 2900 lb force on it—nearly 1.5 TONS slamming against it! It would have shattered or propelled the window!

Stairwell: If only a tenth of the total energy of the above half cup of gasoline was expended in the initial stairwell explosion, would the window stay in place? The stairwell’s glass window would experience 5900 lb force on it—nearly TONS slamming against it! It would have shattered or propelled the window!

Consider that a 4000-lb vehicle (with passengers) may get 32 miles per gallon. One cup of gasoline would provide enough energy or force to drive or instantly propel the vehicle 2 miles, or 10,560 feet. It is not dependent on time; foot-pounds is not time dependent.

Gasoline is a product designed to fuel internal combustion engines. It is a highly volatile liquid, and its vapors can be ignited easily by a spark, flame or other hot object. When mixed with air in the right proportions, the vapor of one cup of gasoline has the explosive power of about five pounds [12 regular sticks] of dynamite, enough destructive force to destroy any house or car.

“Storing Gasoline and Other Flammables” by Timothy G. Prather from University of Tennessee Extension

A Unit Converter

Gallons Gasoline <–> Foot-pounds Force

Plug in different values for amounts of gasoline to get a greater sense of the force of gasoline. Try 0.0625 gallons, which is 1/16 gallon or 1 cup.

The above converter website uses an even greater 97,000,000 foot-pounds per gallon gasoline, instead of the averaged 80,000,000 foot-pounds per gallon value that we’ve on this page.

Recap:

  • A foot-pound is the force or amount of energy required to lift one pound one foot.
  • 1 cup gasoline = 1/16 gal gasoline produces 5,000,000 ft-lb of force, enough force to lift 5,000,000 pounds one foot, or lift one pound 5,000,000 feet. If the average locomotive weighs 470,000 lb, just 1 cup gasoline can lift that locomotive 10 feet!

Thermal Dynamics

Thermal dynamics will be added next.