CHEMICAL DATA NOTEBOOK SERIES #69: GASOLINE
HAZARDOUS MATERIALS
Gasoline is the most common flammable liquid used in the world today. It is used in such quantity that it is amazing that more accidents to not occur. Gasoline is a flammable, volatile, irritating, toxic, nerve-depressing, colorless, amber or pale-brown liquid with a characteristic odor. A mixture of hydrocarbons, it is not a pure substance. Its principal use is as a fuel, but it also has some industrial uses as a solvent. It is a stable compound that is noncorrosive to metals and does not react with water. Gasoline has no chemical formula, since it basically is a mixture of the fiveto 10carbon alkanes (pentane, hexane, heptane, octane, nonane, and decane) and their isomers.
PROPERTIES
Gasoline has a flash point that varies from — 35°F to — 50°F, depending on its grade. All gasolines are formulated to perform in engines requiring slightly different burning characteristics, and they also are formulated to produce flash points that differ according to the coldest temperature that might occur in the geographic regions where they might be used. Its ignition temperature ranges from 536°F to 835°F, again depending on the grade. Gasoline’s rather narrow flammable range is from 1.2 to 7.6 percent, which is one of the properties that makes it an ideal fuel. The wider the flammable range of a gas or the vapors of a flammable or combustible liquid, the more hazardous it is. Gasoline’s narrow flammable range balances its hazards of low flash point and relatively low ignition temperature.
Since gasoline is a mixture of hydrocarbons, it is insoluble in water. Its specific gravity of 0.73 means that it will float on water, whose specific gravity is 1.0. The vapor densities of all the alkane components are greater than 1.0 (pentane, the lightest of the alkane components, has a vapor density of 2.48), which means that the vapors of gasoline (or. more correctly, its components) are all heavier than air, whose vapor density is 1.0. Gasoline boils at temperatures of from 14()°F to 390°F and freezes at temperatures of from — 131°Fto — 140°F.
HAZARDS
Gasoline’s major hazard is flammability. With such low flash points deliberately formulated, there is almost a 100 percent probability that gasoline vapors from a spill will be within the flammable range. Its relatively low ignition temperatures are well within the range of all common ignition sources, and ignition of the vapors of gasoline, like the vapors of all other flammable liquids, will produce an explosion, the strength of which will be determined by the amount of vapors in the air. The narrow flammable range means that near the surface of spilled liquid the vapors may be too rich to burn, but the high vapor density means that the vapors will “hang together” for a long time, flow along low spots in the terrain, and look for an ignition source.
The health hazards of gasoline vary with the additives used. Gasoline containing lead slowly is being phased out of use, but the additives substituted for lead may have different adverse effects. Gasoline’s TLV-TWA (threshold limit value-time weighted average) is 300 ppm (parts per million in air), and its STEL (short-term exposure limit) is 500 ppm. Its threshold odor concentration is 0.25 ppm.
Repeated contact of the liquid with the skin may cause irritation and redness due to the defatting action on the skin, and hypersensitivity may develop in some individuals. Contact with the eyes usually causes temporary injury only.
Inhaling vapors may depress the central nervous system. Low concentrations can cause dizziness, headache, and mental contusion, while high concentrations can cause convulsions, unconsciousness, coma, pulmonary edema, and death from asphyxiation or respiratory failure. Damage also can occur to other organs, including the pancreas, liver, and kidneys.
Ingestion can irritate the mouth, esophagus, and stomach and can depress the central nervous system. Aspiration can severely irritate the lungs and produce pulmonary edema and pneumonitis.
Some gasolines contain benzene as an additive, which is a known carcinogen.
Gasoline, though it is a mixture and not a compound, is still a stable material. Since it is a mixture of hydrocarbons, it reacts in a manner similar to other hydrocarbons—violently or explosively with all strong oxidizers in a gas or vapor form, assuming that some energy source is present.
NONFIRE RELEASE
When gasoline is released accidentally, the procedures for safely handling the incident are the same as those for all flammable liquids.
Approach from upwind, and climinate all ignition sources. Prevent all unauthorized personnel from entering the area, and avoid all bodily contact with the liquid. Respiratory protection also is required.
Prevent gasoline, like other flammable liquids or substances with other hazards, from entering sewers and waterways by blocking catch basins and other entry ways to sewers and by containing the liquid in ponds or pits. Ponds can be constructed by building dikes of soil, sand, clay, or other materials. Also, containment pits and trenches leading the liquid to the pit may be dug. In all cases, sparkproof tools and explosionproof equipment must be used to avoid igniting the vapors.
A pit is more desirable than a containment pond because the pit probably will have a smaller surface area. One of the variables controlling the evolution of vapors (evaporation rate) of liquids is the surface area of the liquid interfacing with the atmosphere. All other factors (temperature, pressure, and so forth) being equal, the larger the surface area, the higher the rate of evaporation. With a smaller surface area, mitigation techniques such as covering with a tarpaulin or blanketing with foam are more feasible.
Firefighting foam is fairly effective in reducing vapor evolution, even with a low flash point like gasoline’s. Tile foam, however, may break down, and reapplication may be necessary. As the foam breaks down, it will add to the volume of the contained liquid and cause a runoff, which also will have to be contained. A fine water spray or fog may be used to accelerate the dispersal of vapors immediately downwind of the spill. This water may be contaminated with gasoline and must be contained, and any spray used in dispersal may add to the volume of the contained product.
When dealing with an accidental release of gasoline, whether contained or not, consider evacuation of local and downwind areas. If the liquid does enter a sewer or waterway and containment by damming or diking the waterway is not possible, notify all downstream users of the water and operators of sewage-treatment facilities. Any intake of water contaminated with gasoline into an industrial operation could cause disastrous explosions.
IDENTIFICATION NUMBERS AND RATINGS
CAS
(Chemical Abstract Services)
8006-61-9
STCC
(Standard Transportation Commodity Code)
4908176, 4908177, 4908178
RTECS
(Registry of Toxic Effects of Chemical Substances) LX3300000
UN/NA
(United Nations/North America)
1203, 1257
CHRIS
(Chemical Hazard Response Information System) GAT
DOT
(U.S. Department of Transportation) flammable liquid
NFPA 704 Rating
1-3-0
IMO
(International Maritime Organization)
3.1, flammable liquid
Since its specific gravity of 0.73 and insolubility in water make it possible for gasoline to float on water, it can be skimmed off the top of a lake or slowmoving stream by conventional floating booms and suctioned into secure containers. One mitigation technique is to dam or dike a waterway and divert the gasoline into a containment area where it can be removed. Again, all tools and equipment must be sparkproof and explosionproof.
Gasoline in containment ponds and pits will tend to percolate into the soil, spreading contamination. At the first indication of a gasoline or any other hazardous-material spill, notify the proper environmental authorities. They must have the final word on cleanup and how far contamination may have spread. Cleanup at hazardous-materials incidents should be done by qualified professionals—and not the fire department —unless, of course, the fire department has been properly educated, trained, and equipped for this task. Cleaning up may be as hazardous as mitigating the incident, and most fire departments are not qualified to do it.
Clay, soil, sand, fly ash. cement powder, peat moss, straw, or commercial sorbents may be used to absorb the spilled liquid. After the material has been absorbed, it is still a hazardous flammable liquid, and the same care must be given to the absorbed material as is given to the spilled product. It should be disposed of by qualified professionals.
FIRE SCENARIO
If a tank truck or other gasoline container is not involved in fire but the container is being threatened by flames or radiant heat, the container must be kept as cool as possible with water applied from as far away as possible and with as little exposure of firefighters as possible. As the container is heated, catastrophic failure of the tank is possible if excess pressure is not vented away. Gasoline tank trucks ordinarily are not subject to a BLEVE (boiling-liquid, expanding-vapor explosion), since the aluminum tank usually will melt or burn away, relieving the pressure. If conditions are just “right,” however, the container can rupture, with the resulting explosion and fire as devastating as a BLEVE.
THE CHEMICAL CLEARINGHOUSE
The Chemical Clearinghouse aims to decrease deaths and injuries among emergency personnel responding to incidents involving chemicals, as well as reduce the damage to the environment, society and its systems, and property that result from such incidents. It will serve as a central agency for collecting and disseminating chemical-related information generally not available to the majority of emergency responders. Appropriate data will be published in Fire Engineering, as urgency determines and space allows. The Clearinghouse does not guarantee that the experiences shared by contributors concerning mitigation techniques or chemical reactions will be the same as those others will encounter during incidents involving the same chemicals. The data are intended to expand responders’ body of knowledge and options aimed at safely and successfully mitigating hazardous-materials incidents.
The data may be submitted by firefighters, members of hazardousmaterials response teams, govern-
ment agencies, private manufacturing companies, or anyone else who has observed a phenomenon, such as a violent or explosive reaction, associated with a particular chemical that has not been reported or is not widely known among emergency responders. The information may betaken from material safety data sheets (MSDSs), manufacturer or government records, reference books or magazines, or any other source.
Material submitted may include the chemical’s physical and other properties, appearance, uses, safe storage and handling procedures, usual shipping form(s), containers (include details such as the materials used to construct the container and whether the container has safetyrelief devices), normal transportation modes, unusual reactions, and procedures for handling a haz-mat incident (the complete report can be submitted).
Information should be sent to Chemical Clearinghouse c/o Fire Engineering, Park 80 West, Plaza II, 7th floor, Saddle Brook, NJ 07662.
Most fire departments have responded to gasoline fires and, therefore, have experience in handling emergencies involving the burning flammable liquid. Great strides have been made with regard to the use of water in these incidents; at one time, the use of water was forbidden because it displaced the burning gasoline and carried it beyond the fire scene. New nozzles that apply water to the fire as a fine spray or fog have allowed new tactics to be used for controlling the burning liquid.
PROTECTIVE CLOTHING AND EQUIPMENT
Choose clothing and protective equipment that prevents gasoline liquid or vapor from contacting the eyes, skin, and respiratory system. Use splashproof chemical goggles and a face shield for eye protection as well as positive-pressure, self-contained breathing apparatus. Rubber boots, gloves, aprons, and other impervious clothing offer protection. Some manufacturers of total encapsulating suits claim that chlorinated polyethylene, neoprene, nitrile-butadiene rubber, nitrile rubber, polyurethane, and Viton® offer protection Protection does not appear to be as major an issue as it might be with other hazardous chemicals because contact with gasoline, while hazardous and damaging to skin, is not as hazardous as many other substances.
SYNONYMS
automotive gasoline aviation gasoline benzin
blended gasoline casinghead gasoline light gasoline motor fuel motor spirit natural gasoline petrol gasolene
FIRST AID
Inhalation. Move the victim to fresh air and keep him/her calm and warm. If breathing has stopped or becomes labored, administer artificial respiration. First-aid givers should be aware that such action might expose them to the material in the victim’s lungs and/or vomit. Immediate medical attention is needed.
Bye contact. Flush the eyes immediately for at least 15 minutes, lifting the eyelids occasionally. Immediate medical attention is required.
Skin contact. Wash the affected areas of the body with large amounts of soap and water. If irritation continues after washing, seek medical attention.
Ingestion. Keep the victim calm and warm; do not induce vomiting. Immediate medical attention is needed.
