Tetrahydrofuran
HAZARDOUS MATERIALS
Chemical Data Notebook Series #22:
Tetrahydrofuran, a solvent for plastics, resins, inks, and pharmaceuticals, is bad enough for responders in its liquid state. It’s narcotic, irritating, volatile, and flammable, and it offers the potential for a violent BLEVE (boiling-liquid, expanding-vapor explosion).
But should THF spill, it becomes even more dangerous, because then it’s subject to slow oxidation upon exposure to air. That could lead to the formation of an unstable, explosive organic peroxide, or result in an explosion caused by runaway polymerization.
Tetrahydrofuran will often be found in industrial operations where polyvinyl chloride or other vinyl resins are converted into film and other shapes that are “cast” rather than extruded. To be cast, the materials need to first be dissolved, and THF is the solvent that does it.
Tetrahydrofuran is colorless, with a faint, etheror acetone-like odor. It has a flash point of – 4° F, a flammable range of 1.8 to 11.8 percent, and an ignition temperature of 610° F. It has a specific gravity of 0.88, a vapor density of 2.48, and a molecular weight of 72. It boils at 149° F, freezes at -163.3° F, and is soluble in water.
The chemical formula is CH2(CH2)2CH2O.
Its ether-like atomic structure gives it two properties of ethers: its distinctive odor and its dangerous propensity to oxidize very slowly in air to form organic peroxides that are even more hazardous.
It’s the vapor that goesthrough this reaction in air. The liquid is more stable in storage, but the less vapor space the better, and no air should be allowed into the vapor space.
Tetrahydrofuran may also polymerize under certain conditions. It may contain trace amounts of additives (stabilizer or inhibitor) to prevent the polymerization and also prevent the peroxide formation. The inhibitor usually used with THF is butylated hydroxytoluene (BHT). P-cresol or hydroquinine may also be used to prevent peroxide formation.
If no peroxides have formed, the compound is somewhat stable. It will, however, react violently with many acids, hydrides, strong oxidizers, and strong bases such as sodium hydroxide and potassium hydroxide.
Tetrahydrofuran vapors are very irritating to the eyes, nose, and lungs, and, in high concentrations, they may be narcotic. Headaches, dizziness, nausea, unconsciousness, and asphyxiation may occur with high concentrations. Chronic exposure to vapor concentrations above 3,000 parts per million of air may cause liver and kidney damage.
Synonyms
Butane, 1.4-epoxy
Butylene oxide
Cyclotetramethylene oxide
Diethylene oxide
1,4-epoxybutane
Furanidine
Hydrofuran
NCI-C60560
Oxacyclopentane
Oxolane
Resource Conservation and Recovery Act Waste Number U213
Tetramethylene oxide
THF
T-397
T-397-S
T-400
T-424
Identification Numbers and Ratings
UN/NA
(United Nations/North America)
2056
National Fire Protection Association 704 rating
2-3-1
CAS
(Chemical Abstract Service)
109-99-9
RTECS
(Registry of Toxic Effects of Chemical Substances)
National Institute of Occupational Safety and Health
LU 5950000
STCC
(Standard Transportation Commodity Code)
Association of American Railroads, Bureau of Explosives)
4908290
CHRIS
(Chemical Hazard Response Information System)
U.S. Coast Guard THF
IMO
(International Maritime Organization)
3.1, flammable liquid
Contact with the skin will cause defatting and eventual cracking of the skin, and contact with the eyes will produce burns and possible blindness. Aspiration into the lungs will cause severe lung irritation and possible chemical pneumonitis. Ingestion will produce irritation of the gastrointestinal tract, nausea, and vomiting. The chemical is an eye and mucous membrane irritant and a central nervous depressant.
Tetrahydrofuran’s odor threshold is 20 ppm, its short-term exposure limit (STEL) is 250 ppm for 15 minutes, and its threshold-limit value/time-weighted average (TLV/TWA) is 200 ppm. A concentration of 20,000 ppm is considered immediately dangerous to life and health (IDLH).
No matter what the spill, approach must always be made from upwind. The very low flash point indicates that, in all but the coldest weather, THF will be producing vapors sufficient to form an ignitable mixture. The very low lower flammable limit indicates the vapors will enter the flammable range quite quickly, and the relatively low ignition temperature indicates that ignition may be initiated by all common sources (which, as in any spill of flammable liquid, must be eliminated immediately).
The high vapor density means that THF vapors will sink to the ground and flow along low spots. It will travel great distances, and may accumulate in the low spots or confined spaces, creating potentially explosive and toxic situations.
Evacuation should be one of the first actions considered. Populated areas downwind should be the first considered, along with areas around a tank of THF that might be threatened by radiant heat of flame impingement from a nearby fire. The size of the container will determine the radius of the evacuation area around this tank, but one-half to one mile is a starting point.
Because the chemical is watersoluble, water sprays or fogs may be used to disperse vapors and dissolve them. However, all runoff water created this way must be contained, since it will contain dissolved THF.
Every effort should be made to keep THF from reaching a sewer or waterway. Catch basins should be diked, and entrances to any waterway must be blocked.
If any liquid does reach a waterway, all downstream users must be warned immediately. Any water drawn into an operation that will be heated or open to the atmosphere will release THF vapors.
The material will dissolve at once upon entrance to a waterway. Efforts should be made to divert water containing the dissolved THF. Once confined, the water may be decontaminated by aeration or sparging. Care must be taken during this process, since the air above the water will contain THF vapors.
Tetrahydrofuran may be collected and prevented from spreading by building containment dikes of sand, clay, soil, or any other material that will hold the liquid in. Trenches may be dug that leaci the liquid from the spill to a containment pond or holding pit dug for the purpose. The equipment used must be spark-proof and explosion-proof. There should be no hot surfaces, electrical switches or connections, or metal that will produce a spark.
Sand, clay, soil, or other absorbent materials may also be used to soak up the material. The sorbents, once saturated with THF, must be disposed of in the same manner as other contaminated material, because they’ll release flammable vapors.
The material may contaminate any soil it contacts, which must be disposed of in accordance with all federal, state, and local regulations.
Usable contaminated liquid may be pumped into secure containers, again using only equipment that won’t provide an ignition source.
Containers exposed to high heat may fail due to increased pressure. If the heat comes from an impinging flame, the pressure may rise faster than it can be relieved by an operating vent or spring-loaded relief valve. Catastrophic failure of the container may follow, releasing tremendous amounts of heated liquid and producing flammable vapors.
If the flame impingement weakens the container’s metal, the rising pressure will tear the metal at that point. If the liquid inside has been heated to a temperature above its boiling point (which isn’t hard to do, with a boiling point of 149° F), the classic conditions for a BLEVE will be established. The resulting explosion will produce a fireball of gigantic proportions, relative to the size of the container. Anyone caught close to the fireball stands little chance of survival.
All containers of THF should be protected from excessive heat, and should be cooled with water if threatened by a fire. The water should be applied from as far away as possible, and with unmanned appliances, if available.
Recommended extinguishing agents include alcohol foam, carbon dioxide, and water spray or fog. What’s used depends on the amount of material spilled, the weather, and the surrounding terrain. Water may not be able to cool THF below its flash point, but, depending on conditions, it may be used to dilute the spill and raise the flash point of the solution.
Since the ignition temperature of THF is so low (610° F), pool fires of the liquid that have been extinguished stand a high probability of being quickly reignited, particularly if any metal has been exposed to the fire.
First aid and protection
Artificial respiration must be administered if breathing has become difficult or stopped altogether. The victim should be removed to fresh air as quickly as possible and medical attention sought immediately.
Should THF come in contact with the skin, all contaminated clothing should be removed at once, and affected areas of the body should be washed as soon as possible. Medical attention will be necessary if irritation of the skin occurs after washing.
Upon eye contact, the eyes should be flushed immediately with water for a minimum of 15 minutes, occasionally lifting the eyelids. Medical attention should be provided at once.
If the material is ingested, vomiting should not be induced, unless there’s no possibility of quick medical attention and the victim is conscious. Never try to induce an unconscious person to vomit.
Protective equipment must be impervious to THF and prevent contact with the eyes and skin. This may include rubber boots and gloves, and splash-proof face shield or goggles. Any articles of clothing should be impervious to THF.
Glossary
Aeration—The process of mixing air with a liquid, sometimes accomplished by spraying the liquid into the air.
Hydride—An ionic compound containing hydrogen and a metal.
Inhibitor—A material added to a polymerizable material to prevent rapid, uncontrolled polymerization.
Organic peroxide—A hydrocarbon derivative that contains the very unstable peroxide radical (-0-0-) between two hydrocarbon radicals.
Oxidizer—A substance that readily gives up its oxygen or otherwise supports combustion.
Polymerize—To form a “giant” molecule by the chemical reaction of “tiny” molecules, called monomers, all of the same type.
Sparging—The act of bubbling air or another gas through another medium.
