Conceptos erróneamente incluidos en la práctica judicial

As mentioned in part one, fire has been described as having three components: fuel, heat, and oxygen. This triad was illustrated by the fire triangle, which symbolized, in the most basic terms, a chemical relationship. The additional component needed to explain flaming combustion is a chemical chain reaction shown in the fire tetrahedron.

FUEL

FUELS (Combustible Materials)– fuel is matter and matter exist in three physical states: solid, liquid and gas.

Solids melt to become liquids, and these may vaporize and become gases. The basic rule is that at high enough temperature all fuels can be converted to gases. And each of the physical states exhibits different physical and chemical properties that directly affect a fuel’s combustibility. For example, gasoline as a liquid does not burn, it is the vapors rising from the liquid that burn. Likewise, wood, the most common solid fuel, is not flammable, but gives of flammable vapors (free radicals).

FUEL is also a material that provides useful energy. Fuels are used to heat and cook food, power engines, and produce electricity. Some fuels occur naturally and others are artificially created. Such natural fuels are coals, petroleum, and natural gases obtained from underground deposits that were formed million years ago from the remains of plants and animals. They are called fossil fuels, which account for about 90% of the energy people use today.

Synthetic fuels can be made from fossil fuels, certain types of rock and sand, and biomass.

Most fuels release energy by burning with oxygen in the air. But some – especially chemical fuels used in rockets – need special oxidizers in order to burn. Nuclear fuels do not burn but release energy through the fission (splitting) of fusion (joining together) of atoms.

Classification of Combustible Materials

1. Class A Fuels – they are ordinary combustible materials that are usually made of organic substances such as wood and wood-based products. It includes some synthetic or inorganic materials like rubber, leather, and plastic products.

2. Class B Fuels – materials that are in the form of flammable liquids such as alcohol, acidic solutions, oil, liquid petroleum products, etc.

3. Class C Fuels – they are normally fire resistant materials such as materials used on electrical wiring and other electrical appliances.

4. Class D Fuels – they are combustible metallic substances such as magnesium, titanium, zirconium, sodium and potassium.

General Categories of Fuel

1. Solid Combustible Materials – includes organic and inorganic, natural or synthetic, and metallic solid materials.

2. Liquid Combustible Materials – includes all flammable liquid fuels and chemicals.

3. Gaseous Substances – includes those toxic/hazardous gases that are capable of ignition.

The Solid Fuels

The most obvious solid fuels are wood, paper and cloth. Its burning rate depends on its configuration. For example, solid fuels in the form of dust will burn faster than bulky materials.

Types of Flammable solids

a. Pyrolyzable solid fuels – include many of the ordinary accepted combustibles: wood, paper and so on. The vapors released by their chemical decomposition support flaming combustion. This exemplifies a gas-to-gas reaction:

the vapors released mixed with oxygen in the air to produce a flame.

b. Non-pyrolyzable solid fuels – solid fuels that are difficult to ignite. A common example is charcoal.

Chemical decomposition does not occur because there are no pyrolyzable elements present. No vapors are released.

The glowing combustion that results is an example of a gas-to-solid reaction.

The following are group of solid fuels

1. Biomass – it is the name given to such replaceable organic matters like wood, garbage and animal manure that can be use to produce energy. For example, heat produced by burning nutshells, rice and oat hulls, and other by-products of food processing. They are often used to operate plant equipment.

Factors affecting the combustibility of wood and wood-based products a. Physical form – the smaller the piece of wood, the easier it is to burn.

b. Moisture content (water content) – the freshly cut wood is more difficult to ignite and burn than dry wood.

c. Heat conductivity - a poor conductor of heat takes a longer time to ignite than those materials that are good conductors of heat.

d. Rate and period of heating – less flammable materials don’t easily ignite and needs direct contact with flame than highly combustible materials.

e. Rate of combustion – with an unlimited supply of oxygen, the rate of burns increases, more heat is produced and fuel is consumed more completely.

f. Ignition temperature – the higher the temperature, the faster it reaches ignition point and it varies depending on the other factors above.

2. Fabrics and Textiles – almost all fibers and textiles are combustible. A fiber is a very fine thin strand or thread like object. Fabrics are twisted or woven fibers. And textiles are machine woven or knitted fabric.

Classification of Fibers

a. Natural Fibers – they come from plants (Coir – coconut fiber, Cotton – seed fiber, pulp – wood fiber) , from animals (wool, silk, protein fibers – leather), from minerals (asbestos)

b. Synthetic/Artificial Fibers – organic fibers, cellulose fibers, cellulose acetate, non-cellulose, and inorganic fibers like fiber glass, steel

Factors affecting the combustibility of fibers

a. Chemical composition – natural and synthetic organic fibers are generally highly combustible materials especially if they are dry. Mineral fibers and synthetic inorganic fibers are normally fire resistant materials.

b. Fiber finish or coating – fiber coating combined with organic fibers are supportive to continued burning of fabric.

c. Fabric weight – the heavier the fabric, the greater its resistance to ignition, thus delaying its ignition.

d. Tightness of weave – the closer the fiber are woven, the smaller the space it contains, thus it takes a longer period to ignite it.

e. Flame retardant treatment – fabric treated with flame retardant have higher resistance to ignition.

Fabric Ignition

Limiting Oxygen Index (LOI) is a numerical basis of measuring the tendency of a fabric to continuously burn once source of ignition is removed. If the LOI of a fabric is high, the probability that it will cease to burn once the flame is removed is also high. Fabrics with high LOI and high ignition temperature are safer for clothing and furnishing because they do not ignite easily. Also, they do not continue burning after the source of heat or flame is removed.

3. Plastics – plastics are included as ordinary fuels under class A except those materials of or containing cellulose nitrate. Cellulose Nitrate is a chemical powder used in bombs, they are also called pyroxylin.

Plastics comprise a group of materials consisting mainly of organic substances or high molecular substances. They are solid in the finished state although at some stage of manufacture plastics can be made to flow into a desired shape, usually through the application of heat or pressure or both.

4. Coal – a black, combustible, mineral solid resulting from the partial decomposition of matter under varying degrees of temperature. They are used as fuels in the production of coal gas, water gas, and many coal compounds.

They are also used to heat buildings and to provide energy for industrial machinery.

The forms of coal are: lignite or brown coal, sub-bituminous coal, bituminous coal, anthracite

Bituminous coal is the most plentiful and important coal used by industry. It contains more carbon and produces more heat than either lignite or sub-bituminous coal. It is also the coal best suited for making coke. Antracite is the least plentiful and hardest coal. It contains more carbon and produces more heat than other coals. However, antracite is difficult to ignite and burns slowly.

5. Peat – It is partially decayed plant matter found in swamps called bags and used as a fuel chiefly in areas where coal and oil are scarce. In Ireland and Scotland, for example, peat is cut formed in blocks, and dried; the dried bloks are then burned to heat homes.

The Liquid Fuels

Liquid fuels are mainly made from Petroleum, but some synthetic liquids are also produced. Petroleum is also called crude oil. They may be refined to produce gasoline, diesel oil, and kerosene. Other fuel oils obtained by refining petroleum to distillate oil and residual oils. Distillate oils are light oils, which are used chiefly to heat homes and small buildings. Residual oils are heavy, and used to provide energy to power utilities, factories and large ships.

Oil-based paint products are also highly flammable liquids. In the process of vaporization, flammable liquids release vapor in much the same way as solid fuels. The rate of vapor is greater for liquids than solids, since liquids have less closely packed molecules. In addition, liquids can release vapor over a wide range, example, gasoline starts to give vapor at –40C (-45 F). This makes gasoline a continuous fire hazard; it produces flammable vapor at normal temperature.

General Characteristics of Liquids

1. They are matters with definite volume but no definite shape.

2. They assume the shape of their vessel because there is free movement of molecules.

3. They are slightly compressible. They are not capable of indefinite expansion, unlike gas.

2 General Groups of Liquid Fuels

1. Flammable liquids – they are liquids having a flash point of 37.8 C (100F) and a vapor pressure not exceeding 40 psia (2068.6 um) at 37.8 C.

2. Combustible Liquids – these liquids have flash point at or above 37.8 C (100F).

Burning Characteristics of Liquids

Since it is the vapors from the flammable liquid which burn, the case of ignition as well as the rate of burning can be related to the physical properties such as vapor pressure, flash point, boiling point, and evaporation rate.

1. Liquids having vapors in the flammable range above the liquid surface at the stored temperature have rapid rate of flame propagation.

2. Liquids having flash points above stored temperature have slower rate of flame propagation. The chemical explanation is, it is necessary for the fire to heat sufficiently the liquid surface to form flammable vapor-air moisture before the flame will spread through the vapor.

Factors affecting the Rate of Flame Propagation and Burning of Liquids

 wind velocity

 temperature

 heat of combustion

 latent heat of evaporation

 atmospheric pressure

Latent heat is the quantity of heat absorbed by a substance from a solid to a liquid and from a liquid to gas.

Conversely, heat is released during conversion of a gas to liquid or liquid to a solid.

The Gas Fuels

Gaseous fuels are those in which molecules are in rapid movement and random motion. They have no definite shape or volume, and assume the shape and volume of their container. There are both natural and manufactured flammable gases. Gas fuels flow easily through pipes and are used to provide energy for homes, businesses, and industries. Examples of gas fuels are acetylene, propane, and butanes.

Some properties of gas fuels are:

 compressibility

 expandability

 permeability (open to passage or penetration)

 diffusion (intermingling of molecules)

Compressibility and expandability refer to the potential in changes in volume. Diffusion is the uniform distribution of molecules of one substance through those of another. Permeability means that other substances may pass through or permeate a gas.

Characteristics of Gas Fuels

1. They are matters that have no definite shape.

2. They are composed of very tiny particles (molecules) at constant random motion in a straight line 3. Gas molecules collide against one another and against the wall of the container and are relatively far

from one another.

Classification of Gases:

1. Based on Source

a. Natural Gas – the gas used to heat buildings, cook food, and provides energy for industries. It consists chiefly of methane, a colorless and odorless gas. Natural gas is usually mixed with compounds of foul-smelling elements like sulfur so gas leaks can be detected. Butane and propane, which make up a small proportion of natural gas, become liquids when placed under large amount of pressure. When pressure is released, they change back to gas. Such fuels, often called Liquefied Petroleum Gas (LPG) or liquefied Natural Gas (LNG), are easily stored and shipped as liquid.

b. Manufactured Gas – this gas like synthetic liquid fuels is used chiefly where certain fuels are abundant and others are scarce. Coal, petroleum, and biomass can all be converted to gas through heating and various chemical procedures.

2. According to Physical Properties

a. Compressed Gas – gas in which at all normal temperature inside its container; exist solely in the gaseous state under pressure. The pressure depends on the pressure to which the container is originally charged and how much gas remains in the container. However, temperature affects the volume and pressure of the gas.

b. Liquefied Gas – gas, which, at normal temperature inside its container, exist partly in the liquid state and partly in gaseous state and under pressure as long as any liquid remains in the container. The pressure basically depends on the temperature of the liquid although the amount of liquid also affects the pressure under some condition. A liquefied gas exhibits a more complicated behavior as the result of heating.

c. Cryogenic Gas – a liquefied gas which exists in its container at temperature far below normal atmospheric temperature, usually slightly above its boiling point and correspondingly low to moderate pressure. Examples of this gas are air, carbon monoxide, ethylene, fluorine, helium, hydrogen, methane, nitrogen, and oxygen.

3. According to Usage

a. Fuel Gases – flammable gases usually used for burning with air to produce heat, utilize as power, light, comfort, and process. Most commonly used gases are natural gas and the LPG (butane and propane).

b. Industrial Gases - This group includes a large number of gases used for industrial processes as those in welding and cutting (oxygen, acetylene); refrigeration (freon, ammonia, sulfur dioxide); chemical processing (hydrogen, nitrogen, ammonia, chlorine); water treatment (chlorine, fluorine).

c. Medical Gases – those used for treatment such as anesthesia (chloroform, nitrous oxide);

respiratory therapy (oxygen).

Burning of Gaseous Fuels

Gaseous fuels are already in the required Vapor State. Only the proper intermixed with oxygen and sufficient heat is needed for ignition. Gases like flammable liquids, always produce a visible flame, they do not smolder.

Chemical Fuels

Chemical fuels, which are produced in solid and liquid form, create great amounts of heat and power. They are used chiefly in rocket engines. Chemical rocket propellants consist of both a fuel and an oxidizer. A common rocket fuel is the chemical hydrazine. The oxidizer is a substance, such as nitrogen tetroxide, that contains oxygen. When the propellant is ignited, the oxidizer provides the oxygen the fuel needs to burn. Chemical fuels are also used in some racing cars.

Nuclear Fuels

Nuclear fuels provide energy through the fission or fusion of their atoms. Uranium is the most commonly used nuclear fuel, though plutonium also provides nuclear energy. When the atoms of these elements undergo fission, they release tremendous amounts of heat. Nuclear fuels are used mainly to generate electricity. They also power some submarines and ships. Nuclear energy can also be produced through the fusion of hydrogen atoms.

 Nuclear Fission – split of the nucleus of atoms

 Nuclear Fusion – combination of two light nuclei of atom