Disclaimer: The information contained in these guidelines is intended for reference purposes only. It provides a summary of information about chemicals that workers may be exposed to in their workplaces. The information contained in these guidelines is current as of date of publication (September, 1996); recommendations may be superseded by new developments in the field of industrial hygiene. Readers are therefore advised to regard these recomendations as general guidelines and to determine whether new information is available.

OCCUPATIONAL SAFETY AND HEALTH GUIDELINE FOR TETRAHYDROFURAN

INTRODUCTION

This guideline summarizes pertinent information about tetrahydrofuran for workers and employers as well as for physicians, industrial hygienists, and other occupational safety and health professionals who may need such information to conduct effective occupational safety and health programs. Recommendations may be superseded by new developments; readers are therefore advised to regard these recommendations as general guidelines and to determine periodically whether new information is available.

SUBSTANCE IDENTIFICATION

* Formula

(C(2)H(4))(2)O

* Structure

(For Structure, see paper copy)

* Synonyms

1,4-Epoxybutane; cyclotetramethylene oxide; hydrofuran; oxacyclopentane; tetramethylene oxide; THF.

* Identifiers

1. CAS: 109-99-9.

2. RTECS: LU5950000.

3. DOT UN: 2056 26.

4. DOT label: Flammable liquid.

* Appearance and odor

Tetrahydrofuran is a colorless, mobile liquid with a faintly fruity, ether-like odor.

CHEMICAL AND PHYSICAL PROPERTIES

* Physical data

1. Molecular weight: 72.12.

2. Boiling point (760 torr): 66 degrees C (151 degrees F).

3. Specific gravity (water = 1): 0.88 at 20 degrees C (68 degrees F).

4. Vapor density (air = 1 at boiling point of tetrahydrofuran): 2.5.

5. Melting point: -108.5 degrees C (-163.3 degrees F).

6. Vapor pressure at 20 degrees C (68 degrees F): 143-145 torr.

7. Solubility: Soluble in water; miscible with alcohols, ethers, ketones, esters, and hydrocarbons.

8. Evaporation rate (butyl acetate = 1): 8.

* Reactivity

1. Conditions contributing to instability: Heat and sunlight. When exposed to air, unstabilized tetrahydrofuran forms unstable peroxides that may spontaneously explode when their concentrations exceed 1 percent.

2. Incompatibilities: Contact of tetrahydrofuran with strong oxidizing agents may cause explosions. Tetrahydrofuran may polymerize in the presence of cationic initiators. Contact with lithium aluminum hydride, other lithium-aluminum alloys, or with sodium or potassium hydroxide can be hazardous if peroxides are present. Refluxing with calcium hydroxide can cause explosions.

3. Hazardous decomposition products: Toxic gases and vapors may be released in a fire involving tetrahydrofuran.

4. Special precautions: Before distilling or evaporating tetrahydrofuran, it should be tested for peroxides; if tests show that more than 0.05 percent peroxide is present, the tetrahydrofuran should not be distilled.

* Flammability

The National Fire Protection Association has assigned a flammability rating of 3 (severe fire hazard) to tetrahydrofuran.

1. Flash point: -14 degrees C (6 degrees F).

2. Autoignition temperature: 321 degrees C (610 degrees F).

3. Flammable limits in air (percent by volume): Lower, 2; upper, 11.8.

4. Extinguishant: Use dry chemical or carbon dioxide to fight fires involving tetrahydrofuran. Water may be ineffective, but it may be used to cool fire-exposed containers. If a leak or spill has not ignited, water spray may be used to disperse vapors and to protect persons attempting to stop the leak.

Fires involving tetrahydrofuran should be fought upwind and from the maximum distance possible. Keep unnecessary people away; isolate hazard area and deny entry. Emergency personnel should stay out of low areas and ventilate closed spaces before entering. Vapor explosion and poison hazards may occur indoors, outdoors, or in sewers. Vapors may travel to a source of ignition and flash back. Containers of tetrahydrofuran may explode in the heat of the fire and should be moved from the fire area if it is possible to do so safely. If this is not possible, cool containers from the sides with water until well after the fire is out. Stay away from the ends of containers. Personnel should withdraw immediately if a rising sound from a venting safety device is heard or if there is discoloration of a container due to fire. Dikes should be used to contain fire-control water for later disposal. If a tank car or truck is involved in a fire, personnel should isolate an area of a half a mile in all directions. Firefighters should wear a full set of protective clothing, including a self-contained breathing apparatus, when fighting fires involving tetrahydrofuran. Firefighters' protective clothing may provide limited protection against fires involving tetrahydrofuran.

* Warning properties

The best estimates of the odor recognition/detection thresholds for tetrahydrofuran are 31/61 parts per million (ppm) parts of air. Because these values are below the Occupational Safety and Health Administration (OSHA) current permissible exposure limit (PEL) of 200 ppm, tetrahydrofuran is considered to have adequate warning properties for the purpose of respirator selection.

* Eye irritation properties

No information is available on the specific concentration of tetrahydrofuran at which eye irritation begins; however, this substance is known to be an eye irritant.

EXPOSURE LIMITS

The current Occupational Safety and Health Administration (OSHA) PELs for tetrahydrofuran are 200 ppm (590 milligrams per cubic meter (mg/m³)) as an 8-hour time-weighted average (TWA) concentration and 250 ppm (735 mg/m³) as a 15-minute TWA short-term exposure limit (STEL). A STEL is the maximum 15-minute concentration to which workers may be exposed during any 15-minute period of the working day [29 CFR 1910.1000, Table Z-1-A]. The National Institute for Occupational Safety and Health (NIOSH) has not issued a recommended exposure limit (REL) for tetrahydrofuran; however, NIOSH concurs with the PEL established for this substance by OSHA [NIOSH 1988]. The American Conference of Governmental Industrial Hygienists (ACGIH) has assigned tetrahydrofuran a threshold limit value (TLV) of 200 ppm (590 mg/m³) as a TWA for a normal 8-hour workday and a 40-hour workweek and a short-term exposure limit (STEL) of 250 ppm (737 mg/m³) for periods not to exceed 15 minutes [ACGIH 1989, p. 35]. The OSHA and ACGIH limits are based on the risk of systemic effects associated with exposure to tetrahydrofuran.

HEALTH HAZARD INFORMATION

* Routes of exposure

Exposure to tetrahydrofuran can occur via inhalation, ingestion, and eye or skin contact [Sittig 1985, p. 848].

* Summary of toxicology

1. Effects on Animals: Tetrahydrofuran is an irritant of the eyes, nose, and upper respiratory tract and, at high concentrations, a depressant of the central nervous system. It also causes liver damage in exposed animals. The LC(50) in rats is 21,000 ppm for 3 hours, and the oral LD(50) in the same species is 2816 mg/kg [RTECS 1989]. Mice exposed to a tetrahydrofuran concentration of 22,000 ppm for 2 hours died; symptoms preceding death included profuse salivation, a marked fall in blood pressure, respiratory stimulation, and poor muscular relaxation [Gosselin 1984, p. II-408]. Rats exposed to 100 or 200 ppm concentrations of tetrahydrofuran developed redness of the eyelids and nose; when the concentration was increased to 5000 ppm, edema and opacity of the cornea occurred [HSDB 1989]. If tetrahydrofuran solutions that exceed concentrations of 20 percent are applied to rabbit skin, they cause irritation [ACGIH 1986, p. 564]. Animals exposed to more than 3000 ppm for 8 hours/day for 20 days showed signs of upper respiratory tract irritation [Hathaway, Proctor, Hughes, and Fischman 1991, p. 537]. Dogs exposed to a 200-ppm concentration of tetrahydrofuran for 6 hours/day for 3 to 4 weeks exhibited a fall in pulse pressure but did not show histopathological changes at autopsy [ACGIH 1986, p. 564]. Rats exposed to a 1000-ppm concentration of tetrahydrofuran for 4 hours/day for 12 weeks had test results indicating impaired liver function; exposure to 5000 ppm on the same regimen caused morphological damage to the respiratory mucosa, depressed white blood cell counts and blood sugar levels, and affected liver function [HSDB 1989].

2. Effects on Humans: Tetrahydrofuran is a central nervous system depressant in humans; based on effects seen in animals, it may also cause irritation of the mucous membranes and upper respiratory tract and liver and kidney damage. There are no reports of chronic effects in humans [Hathaway, Proctor, Hughes, and Fischman 1991, p. 537]. However, investigators exposed to unknown concentrations while testing tetrahydrofuran's pharmacological properties developed severe occipital headaches [Gosselin 1984, p. II-408]. Researchers engaged in the experimental spinning of synthetic fibers showed a marked decrease in white blood cell count that is believed to have been caused by exposure to tetrahydrofuran, which was used as a solvent; these individuals recovered after 2 years of treatment [HSDB 1989].

* Signs and symptoms of exposure

1. Acute exposure: The signs and symptoms of acute overexposure to tetrahydrofuran include severe headache and a marked decrease in white blood cell count. Based on effects seen in animals, exposure to tetrahydrofuran may cause redness and inflammation of the eyes and eyelids; coughing and sneezing; and difficult breathing.

2. Chronic exposure: No effects of chronic exposure to tetrahydrofuran have been reported in humans. However, based on effects seen in animals, this substance may cause liver damage.

* Emergency procedures:

In the event of an emergency, remove the victim from further exposure, send for medical assistance, and initiate the following emergency procedures:

1. Eye exposure: If tetrahydrofuran or a solution containing this substance gets into the eyes, immediately flush the eyes with large amounts of water for a minimum of 15 minutes, lifting the lower and upper lids occasionally. If irritation persists, get medical attention as soon as possible.

2. Skin exposure: If tetrahydrofuran or a solution containing this substance contacts the skin, the contaminated skin should be flushed with large amounts of water for at least 15 minutes, followed by washing with soap and water. If irritation persists, get medical attention.

3. Inhalation: If tetrahydrofuran vapors are inhaled, move the victim at once to fresh air and get medical care as soon as possible. If the victim is not breathing, perform cardiopulmonary resuscitation; if breathing is difficult, give oxygen. Keep the victim warm and quiet until medical help arrives.

4. If tetrahydrofuran is ingested, DO NOT INDUCE VOMITING. Instead, give the victim several glasses of water to drink and get medical help immediately. Keep the victim warm and quiet until medical help arrives.

5. Rescue: Remove an incapacitated worker from further exposure and implement appropriate emergency procedures (e.g., those listed on the Material Safety Data Sheet required by OSHA's Hazard Communication Standard, 29 CFR 1910.1200). All workers should be familiar with emergency procedures and the location and proper use of emergency equipment.

EXPOSURE SOURCES AND CONTROL METHODS

The following operations may involve tetrahydrofuran and lead to worker exposures to this substance:

* Use as a solvent in the preparation of polyvinyl chloride films and coatings such as those used to form the food-contact surface of food-processing articles and those used to coat magnetic tape
* Use as a solvent in the preparation of adhesives, lacquers, printing inks, fat oils, and unvulcanized rubber
* Use as a reagent for Grignard reaction-based production of tetraethyl and tetramethyl lead and for metal hydride reactions
* Use as a chemical intermediate in the preparation of polytetramethylene glycol; butyrolactone; succinic acid; adipic acid; 1,4 butanediol diacetate; and tetrahydrothiophene, and formerly as an intermediate in the preparation of adiponitrile
* Use as a reaction medium for histological techniques, as a Lewis base to moderate the extreme reactivity of sulfite ion, and as an agent in liquid membrane electrode manufacture

Methods that are effective in controlling worker exposures to tetrahydrofuran, depending on the feasibility of implementation, are

* Process enclosure,
* Local exhaust ventilation,
* General dilution ventilation, and
* Personal protective equipment.

The following publications are good sources of information on control methods:

1. ACGIH [1986]. Industrial ventilation--a manual of recommended practice. Cincinnati, OH: American Conference of Governmental Industrial Hygienists.

2. Burton DJ [1986]. Industrial ventilation--a self study companion. Cincinnati, OH: American Conference of Governmental Industrial Hygienists.

3. Alden JL, Kane JM [1982]. Design of industrial ventilation systems. New York, NY: Industrial Press, Inc.

4. Wadden RA, Scheff PA [1987]. Engineering design for control of workplace hazards. New York, NY: McGraw-Hill.

5. Plog BA [1988]. Fundamentals of industrial hygiene. Chicago, IL: National Safety Council.

MEDICAL MONITORING

Workers who may be exposed to chemical hazards should be monitored in a systematic program of medical surveillance that is intended to prevent occupational injury and disease. The program should include education of employers and workers about work-related hazards, placement of workers in jobs that do not jeopardize their safety or health, early detection of adverse health effects, and referral of workers for diagnosis and treatment. The occurrence of disease or other work-related adverse health effects should prompt immediate evaluation of primary preventive measures (e.g., industrial hygiene monitoring, engineering controls, and personal protective equipment). A medical monitoring program is intended to supplement, not replace, such measures. To place workers effectively and to detect and control work-related health effects, medical evaluations should be performed (1) before job placement, (2) periodically during the period of employment, and (3) at the time of job transfer or termination.

* Preplacement medical evaluation

Before a worker is placed in a job with a potential for exposure to tetrahydrofuran, the examining physician should evaluate and document the worker's baseline health status with thorough medical, environmental, and occupational histories, a physical examination, and physiologic and laboratory tests appropriate for the anticipated occupational risks. These should concentrate on the function and integrity of the skin, respiratory system, and central nervous system. Medical monitoring for respiratory disease should be conducted using the principles and methods recommended by NIOSH and the American Thoracic Society.

A preplacement medical evaluation is recommended to assess an individual's suitability for employment at a specific job and to detect and assess medical conditions that may be aggravated or may result in increased risk when a worker is exposed to tetrahydrofuran at or below the prescribed exposure limit. The examining physician should consider the probable frequency, intensity, and duration of exposure as well as the nature and degree of any applicable medical condition. Such conditions (which should not be regarded as absolute contraindications to job placement) include a history and other findings consistent with diseases of the skin, respiratory system, or central nervous system.

* Periodic medical examinations and biological monitoring

Occupational health interviews and physical examinations should be performed at regular intervals during the employment period, as mandated by any applicable Federal, State, or local standard. Where no standard exists and the hazard is minimal, evaluations should be conducted every 3 to 5 years or as frequently as recommended by an experienced occupational health physician. Additional examinations may be necessary if a worker develops symptoms attributable to tetrahydrofuran exposure. The interviews, examinations, and medical screening tests should focus on identifying the adverse effects of tetrahydrofuran on the skin, respiratory system, or central nervous system. Current health status should be compared with the baseline health status of the individual worker or with expected values for a suitable reference population.

Biological monitoring involves sampling and analyzing body tissues or fluids to provide an index of exposure to a toxic substance or metabolite. No biological monitoring test acceptable for routine use has yet been developed for tetrahydrofuran.

* Medical examinations recommended at the time of job transfer or termination

The medical, environmental, and occupational history interviews, the physical examination, and selected physiologic or laboratory tests that were conducted at the time of placement should be repeated at the time of job transfer or termination to determine the worker's medical status at the end of his or her employment. Any changes in the worker's health status should be compared with those expected for a suitable reference population. Because occupational exposure to tetrahydrofuran may cause diseases with prolonged latent periods, the need for medical monitoring may extend well beyond the termination of employment.

WORKPLACE MONITORING AND MEASUREMENT PROCEDURES

Determination of a worker's exposure to airborne tetrahydrofuran is made using a charcoal tube (100/50 mg sections, 20/40 mesh). Samples are collected at a maximum flow rate of 0.2 liter per minute until a maximum air volume of 9 liters (TWA) and 3 liters (STEL) are collected. The sample is then treated with carbon disulfide to extract the tetrahydrofuran. Analysis is conducted by gas chromatography using a flame ionization detector. This method is described in NIOSH Method No. 1609 [NIOSH 1985].

PERSONAL HYGIENE PROCEDURES

If tetrahydrofuran contacts the skin, workers should immediately wash the affected areas with soap and water.

Clothing contaminated with tetrahydrofuran should be removed immediately, and provisions should be made for the safe removal of the chemical from the clothing. Persons laundering the clothes should be informed of the hazardous properties of tetrahydrofuran, particularly its potential to cause irritation of the eyes, nose, and respiratory tract.

A worker who handles tetrahydrofuran should thoroughly wash hands, forearms, and face with soap and water before eating, using tobacco products, or using toilet facilities.

Workers should not eat, drink, or use tobacco products in areas where tetrahydrofuran or a solution containing tetrahydrofuran is handled, processed, or stored.

STORAGE

Tetrahydrofuran (with an inhibitor) should be stored in a cool, dry, well-ventilated area in tightly sealed metal or amber glass containers that are labeled in accordance with OSHA's Hazard Communication Standard. Storage areas must meet requirements for an OSHA Class IB flammable liquid. Outside or detached storage is preferred; inside storage should be in a standard flammable liquids storage area or room. Containers of tetrahydrofuran should be protected from physical damage and should be stored separately from oxidizers, heat, sparks, and open flame. Drums must be equipped with self-closing valves, pressure vacuum bungs, and flame arrestors. Only nonsparking tools may be used to handle tetrahydrofuran. To prevent static sparks, containers should be grounded and bonded for transfers. Because containers that formerly contained tetrahydrofuran may still hold product residues, they should be handled appropriately.

SPILLS AND LEAKS

In the event of a spill or leak involving tetrahydrofuran, persons not wearing protective equipment and clothing should be restricted from contaminated areas until cleanup has been completed. The following steps should be undertaken following a spill or leak:

1. Do not touch the spilled material; stop the leak if it is possible to do so without risk.

2. Notify safety personnel.

3. Remove all sources of heat and ignition.

4. Ventilate potentially explosive atmospheres.

5. Water spray may be used to reduce vapors, but the spray may not prevent ignition in closed spaces.

6. Use nonsparking tools for cleanup.

7. For small liquid spills, take up with sand or other noncombustible absorbent material and place into closed containers for later disposal.

8. For large liquid spills, build dikes far ahead of the spill to contain the tetrahydrofuran for later reclamation or disposal.

EMERGENCY PLANNING, COMMUNITY RIGHT-TO-KNOW, AND HAZARDOUS WASTE

MANAGEMENT REQUIREMENTS

The Environmental Protection Agency's (EPA's) regulatory requirements for emergency planning, community right-to-know, and hazardous waste management may vary over time. Users are therefore advised to determine periodically whether new information is available.

* Emergency planning requirements

Tetrahydrofuran is not subject to EPA emergency planning requirements under the Superfund Amendments and Reauthorization Act (SARA) (Title III).

* Reportable quantity requirements (releases of hazardous substances)

A hazardous substance release is defined by EPA as any spilling, pumping, pouring, emitting, emptying, discharging, injecting, escaping, leaching, dumping, or disposing into the environment (including the abandonment or discarding of containers) of hazardous substances. In the event of a release that is above the reportable quantity for that chemical, employers are required by the Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA) to notify the proper Federal authorities.

The reportable quantity for tetrahydrofuran is 1,000 pounds. If an amount equal to or greater than this quantity is released within a 24-hour period, CERCLA requires employers to notify the National Response Center IMMEDIATELY at (800) 424-8802 (in Washington, D.C. at (202) 426-2675).

* Community right-to-know requirements

Employers are not required by Section 313 of the Superfund Amendments and Reauthorization Act (SARA) to submit a Toxic Chemical Release Inventory form (Form R) to EPA reporting the amount of tetrahydrofuran emitted or released from their facility annually.

* Hazardous waste management requirements

EPA considers a waste to be hazardous if it exhibits any of the following characteristics: ignitability, corrosivity, reactivity, or toxicity, as defined in 40 CFR 261.21-261.24. Under the Resource Conservation and Recovery Act (RCRA), EPA has specifically listed many chemical wastes as hazardous. Tetrahydrofuran is listed as a hazardous waste under RCRA and has been assigned EPA Hazardous Waste No. U213. This substance has been banned from land disposal and may be treated by fuel substitution or incineration. Tetrahydrofuran also may be disposed of in an organometallic or organic lab pack that meets the requirements of 40 CFR 264.316 or 265.316.

Providing more information about the removal and disposal of specific chemicals is beyond the scope of this guideline. EPA, U.S. Department of Transportation, and State and local regulations should be followed to ensure that removal, transport, and disposal of this substance are conducted in accordance with existing regulations. To be certain that chemical waste disposal meets EPA regulatory requirements, employers should address any questions to the RCRA hotline at (202) 382-3000 (in Washington, D.C.) or toll-free at (800) 424-9346 (outside Washington, D.C.). In addition, relevant State and local authorities should be contacted for information on any requirements they may have for the waste removal and disposal of this substance.

RESPIRATORY PROTECTION

* Conditions for respirator use

Good industrial hygiene practice requires that engineering controls be used where feasible to reduce workplace concentrations of hazardous materials to the prescribed exposure limit. However, some situations may require the use of respirators to control exposure. Respirators must be worn if the ambient concentration of tetrahydrofuran exceeds prescribed exposure limits. Respirators may be used (1) before engineering controls have been installed, (2) during work operations such as maintenance or repair activities that involve unknown exposures, (3) during operations that require entry into tanks or closed vessels, and (4) during emergency situations. If the use of respirators is necessary, the only respirators permitted are those that have been approved by NIOSH and the Mine Safety and Health Administration (MSHA).

* Respiratory protection program

Employers should institute a complete respiratory protection program that, at a minimum, complies with the requirements of OSHA's Respiratory Protection Standard. Such a program must include respirator selection (see Table 1), an evaluation of the worker's ability to perform the work while wearing a respirator, the regular training of personnel, fit testing, periodic workplace monitoring, and regular respirator maintenance, inspection, and cleaning. The implementation of an adequate respiratory protection program (including selection of the correct respirator) requires that a knowledgeable person be in charge of the program and that the program be evaluated regularly. For additional information on the selection and use of respirators and on the medical screening of respirator users, consult the NIOSH Respirator Decision Logic and the NIOSH Guide to Industrial Respiratory Protection.

Table 1 lists the respiratory protection that NIOSH recommends for workers exposed to tetrahydrofuran. The recommended protection may vary over time because of changes in the exposure limit for tetrahydrofuran or in respirator certification requirements. Users are therefore advised to determine periodically whether new information is available.

PERSONAL PROTECTIVE EQUIPMENT

Protective clothing should be worn to prevent skin contact with tetrahydrofuran. Chemical protective clothing should be selected on the basis of available performance data, manufacturers' recommendations, and evaluation of the clothing under actual conditions of use. The following material has been recommended for use against permeation by tetrahydrofuran and may provide protection for periods greater than 8 hours: Teflon. A material that may withstand permeation for more than 4 but fewer than 8 hours is a mixture of polyethylene/ethylene vinyl alcohol. The following materials are not recommended for periods greater than 1 hour: butyl rubber, natural rubber, neoprene, nitrile rubber, polyethylene, polyvinyl chloride, Viton, or Saranex.

If tetrahydrofuran is dissolved in water or an organic solvent, the permeation properties of both the solvent and the mixture must be considered when selecting personal protective equipment and clothing.

Safety glasses, goggles, or faceshields should be worn during operations in which tetrahydrofuran might contact the eyes (e.g., through splashes of solution). Eyewash fountains and emergency showers should be available within the immediate work area whenever the potential exists for eye or skin contact with tetrahydrofuran. Contact lenses should not be worn if the potential exists for tetrahydrofuran exposure.

REFERENCES

ACGIH [1986]. Documentation of the threshold limit values and biological exposure indices. 5th edition. Cincinnati, OH: American Conference of Governmental Industrial Hygienists.

ACGIH [1991]. TLVs. Threshold limit values and biological exposure indices for 1991-1992. Cincinnati, OH: American Conference of Governmental Industrial Hygienists.

[CFR]. Code of Federal regulations. Title 29 (Department of Labor), Parts 1910.1000 and 1910.1200. Washington, DC: U.S. Government Printing Office, Office of the Federal Register.

[CFR]. Code of Federal regulations. Title 40 (Protection of Environment). Washington, DC: U.S. Government Printing Office, Office of the Federal Register.

Gosselin RE, Smith RP, Hodge HC [1984]. Clinical toxicology of commercial products. 5th edition. Baltimore, MD: Williams & Wilkins.

Hathaway GJ, Proctor NH, Hughes JP, and Fischman, ML [1991]. Proctor and Hughes' chemical hazards of the workplace. 3rd edition. New York, NY: Van Nostrand Reinhold.

HSDB [1989]. Tetrahydrofuran. Bethesda, MD: The Hazardous Substances Data Bank, National Library of Medicine.

NIOSH [1985 update]. NIOSH manual of analytical methods. 3rd edition, Volume 1. Cincinnati, OH: U.S. Department of Health and Human Services, Public Health Service, Centers for Disease Control, National Institute for Occupational Safety and Health.

NIOSH [1987a]. NIOSH guide to industrial respiratory protection. Cincinnati, OH: U.S. Department of Health and Human Services, Public Health Service, Centers for Disease Control, National Institute for Occupational Safety and Health. DHHS (NIOSH) Publication No. 87-116.

NIOSH [1987c]. Respirator decision logic. Cincinnati, OH: U.S. Department of Health and Human Services, Public Health Service, Centers for Disease Control, National Institute for Occupational Safety and Health. DHHS (NIOSH) Publication No. 87-108.

NIOSH [1988]. Testimony of the National Institute for Occupational Safety and Health on the Occupational Safety and Health Administration's proposed rule: 29 CFR 1910, Docket No. H-020, August 2, 1988. NIOSH policy statements. Cincinnati, OH: U.S. Department of Health and Human Services, Public Health Service, Centers for Disease Control, National Institute for Occupational Safety and Health.

BIBLIOGRAPHY

ACGIH [1986]. Documentation of the threshold limit values and biological exposure indices. 5th edition. Cincinnati, OH: American Conference of Governmental Industrial Hygienists.

AIHA [1989]. Odor thresholds for chemicals with established occupational health standards. Akron, OH: American Industrial Hygiene Association.

Bretherick L [1985]. Handbook of reactive chemical hazards. 3rd edition. London, England: Butterworths.

[CFR]. Code of Federal regulations. Title 49 (Department of Transportation). Washington, D.C.: U.S. Government Printing Office, Office of the Federal Register.

DOT [1987]. 1987 Emergency response guidebook, guide 26. Washington, DC: U.S. Department of Transportation, Office of Hazardous Materials Transportation, Research and Special Programs Administration.

Forsberg K, Mansdorf SZ [1989]. Quick selection guide to chemical protective clothing. New York, NY: Van Nostrand Reinhold.

Hathaway GJ, Proctor NH, Hughes JP, and Fischman, ML [1991]. Proctor and Hughes' chemical hazards of the workplace. 3rd edition. New York, NY: Van Nostrand Reinhold.

Hawley's condensed chemical dictionary [1987]. Sax NI, Lewis RJ. 11th edition. New York, NY: Van Nostrand Reinhold Company.

Hazardous Substance Fact Sheet [1986]. Tetrahydrofuran. Trenton, NJ: New Jersey Department of Health.

HSDB [1989]. Tetrahydrofuran. Bethesda, MD: The Hazardous Substances Data Bank, National Library of Medicine.

Material Safety Data Sheet No. 379 [1985]. Schenectady, NY: Genium Publishing Corporation.

NFPA [1986]. Fire protection guide on hazardous materials. 9th edition. Quincy, MA: National Fire Protection Association.

Proctor NH, Hughes JP [1978]. Chemical hazards of the workplace. Philadelphia, PA: J.B. Lippincott Company.

RTECS [1989]. Tetrahydrofuran. Bethesda, MD: Registry of Toxic Effects of Chemical Substances, National Library of Medicine.

Sax NI, Lewis RJ [1989]. Dangerous properties of industrial materials. 7th edition. New York, NY: Van Nostrand Reinhold Company.

Sittig M [1985]. Handbook of toxic and hazardous chemicals. 2nd edition. Park Ridge, NJ: Noyes Publications.

Condition	Minimum respiratory protection**
Airborne concentration of tetrahydrofuran:
200 to 1000(+) ppm (5 × PEL)	Any air-purifying respirator equipped with organic vapor cartridges, or Any powered, air-purifying respirator equipped with organic vapor cartridges
200 to 2000 ppm (10 × PEL)	Any supplied-air respirator equipped with a half mask and operated in a demand (negative-pressure) mode
200 to 5000(++) ppm (25 × PEL)	Any air-purifying, full-facepiece respirator equipped with an organic vapor canister, or Any powered, air-purifying respirator equipped with a loose-fitting hood or helmet and an organic vapor canister, or Any powered, air-purifying respirator equipped with a tight-fitting facepiece and an organic vapor canister, or Any supplied-air respirator equipped with a full facepiece and operated in a demand (negative-pressure) mode, or Any supplied-air respirator equipped with a hood or helmet and operated in a continuous-flow mode, or Any supplied-air respirator equipped with a tight-fitting facepiece and operated in a continuous-flow mode, or Any supplied-air respirator operated in a pressure-demand or other positive-pressure mode, or Any self-contained respirator equipped with a full facepiece and operated in a demand (negative-pressure) mode
Entry into unknown concentrations	Any self-contained respirator equipped with a full facepiece and operated in a pressure-demand or other positive-pressure mode, or Any supplied-air respirator equipped with a full facepiece and operated in a pressure-demand or other positive-pressure mode in combination with an auxiliary self-contained breathing apparatus operated in a pressure-demand or other positive-pressure mode
Firefighting	Any self-contained respirator equipped with a full facepiece and operated in a pressure-demand or other positive-pressure mode
Escape	Any air-purifying, full-facepiece respirator equipped with an organic vapor canister, or Any escape-type, self-contained breathing apparatus with a suitable service life (number of minutes required to escape the environment)

* The OSHA PEL is 200 ppm (590 mg/m³) as an 8-hour TWA. No NIOSH REL has been issued.
** Only NIOSH/MSHA-approved equipment should be used. Also note the following:

1. Respirators accepted for use at higher concentrations may be used at lower concentrations; respirators must not, however, be used at concentrations higher than those for which they are approved.

2. Air-purifying respirators may not be used in oxygen-deficient atmospheres or in airborne concentrations that are immediately dangerous to life or health (IDLH).

(+) The maximum use concentration for organic vapor cartridges is 1000 ppm. Tetrahydrofuran has been reported to cause eye irritation or damage; may require eye protection.
(++) Represents 25 percent of the lower explosive limit.