Disclaimer: These guidelines were developed under contract using generally accepted secondary sources. The protocol used by the contractor for surveying these data sources was developed by the National Institute for Occupational Safety and Health (NIOSH), the Occupational Safety and Health Administration (OSHA), and the Department of Energy (DOE). The information contained in these guidelines is intended for reference purposes only. None of the agencies have conducted a comprehensive check of the information and data contained in these sources. It provides a summary of information about chemicals that workers may be exposed to in their workplaces. The secondary sources used for supplements 111 and 1V were published before 1992 and 1993, respectively, and for the remainder of the guidelines the secondary sources used were published before September 1996. This information may be superseded by new developments in the field of industrial hygiene. Therefore readers are advised to determine whether new information is available.

OCCUPATIONAL SAFETY AND HEALTH GUIDELINE FOR HYDROGEN FLUORIDE

INTRODUCTION

This guideline summarizes pertinent information about hydrogen fluoride 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 Recommendations may be superseded by new developments in these fields; readers are therefore advised to regard these recommendations as general guidelines and to determine whether new information is available.

SUBSTANCE IDENTIFICATION

* Formula

HF

* Structure

(For Structure, see paper copy)

* Synonyms

Anhydrous hydrofluoric acid, antisal 2B, hydrofluoride, hydrofluoric acid, fluorhydric acid, fluoric acid

* Identifiers

1. CAS No.: 7664-39-3

2. RTECS No.: MW7875000; (also listed as MW7890000)

3. DOT UN: 1052 15 (anhydrous), 1790 59 (solution)

4. DOT label: Corrosive, poison (anhydrous)

* Appearance and odor

Hydrogen fluoride is a colorless, fuming liquid or gas (depending on the temperature) with a strong, irritating odor. The air odor threshold for hydrogen fluoride is 0.042 part per million (ppm) parts of air.

CHEMICAL AND PHYSICAL PROPERTIES

* Physical data

1. Molecular weight: 20.01

2. Boiling point (at 760 mm Hg): 19.51 degrees C (67.2 degrees F)

3. Specific gravity: 0.987 at 20 degrees C (68 degrees F)

4. Vapor density: 0.92

5. Melting point: -83.1 degrees C (-117.58 degrees F)

6. Vapor pressure at 2.5 degrees C (36.5 degrees F): 400 mm Hg

7. Solubility: Very soluble in water, in alcohol, and in most organic solvents; slightly soluble in ether.

8. Evaporation rate: Data not available.

* Reactivity

Conditions contributing to instability: Exposure to moisture or steam may produce highly explosive hydrogen gas. Reactions may also occur in the presence of heat and light.

1. Incompatibilities: Contact between hydrogen fluoride and metals, concrete, glass, strong bases, sodium hydroxide, potassium hydroxide, and ceramics may result in reactions.

2. Hazardous decomposition products: Toxic gases and vapors such as fluorine may be released in a fire involving hydrogen fluoride.

4. Special precautions: Store in containers composed of non-corrosive materials, such as lead and wax. The corrosive action on metals can result in the formation of hydrogen gas.

* Flammability

Hydrogen fluoride is a nonflammable gas .

The National Fire Protection Association has assigned a flammability rating of 0 (minimal fire hazard) to hydrogen fluoride.

1. Flash point: Not applicable.

2. Autoignition temperature: Not applicable.

3. Flammable limits in air: Not applicable.

4. Extinguishant: For small fires use dry chemical or carbon dioxide for fires that include anhydrous hydrogen fluoride. For small fires that involve the hydrogen fluoride solution use dry chemical, carbon dioxide, water spray or regular foam. Use water spray, fog, or regular foam to fight large fires involving both phases of hydrogen fluoride.

Fires involving hydrogen fluoride should be fought upwind from the maximum distance possible. Keep unnecessary people away; isolate the hazard area and deny entry. Isolate the area for at least 150 feet in all directions until gas has dispersed. Emergency personnel should stay out of low areas and ventilate closed spaces before entering. Containers of hydrogen fluoride 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 fire exposed containers from the sides with water until well after the fire is out. Do not get water inside the containers. Stay away from the ends of containers. Firefighters should wear a full set of chemical protective clothing and self-contained breathing apparatus when fighting fires involving hydrogen fluoride.

EXPOSURE LIMITS

* OSHA PEL

The current Occupational Safety and Health Administration (OSHA) permissible exposure limit (PEL) for hydrogen fluoride is 3 ppm() as an 8-hour time-weighted average (TWA) concentration [29 CFR 1910.1000, Table Z-2].

* NIOSH REL

The National Institute for Occupational Safety and Health (NIOSH) has established a recommended exposure limit (REL) for hydrogen fluoride of 3 ppm (2.5 mg/m(3)) as a TWA for up to a 10-hour workday and a 40-hour workweek and a short-term exposure limit (STEL) of 6 ppm (5 mg/m(3)) [NIOSH 1992].

* ACGIH TLV

The American Conference of Governmental Industrial Hygienists (ACGIH) has assigned hydrogen fluoride a ceiling limit value of 3 ppm (2.6 mg/m(3)), which should not be exceeded during any part of the working exposure [ACGIH 1994, p. 23].

* Rationale for Limits

The NIOSH limit is based on the risk of skin, eye, and airway irritation; and on effects on bone tissue [NIOSH 1992].

The ACGIH limit is based on the risk of irritation [ACGIH 1991, p. 781].

HEALTH HAZARD INFORMATION

* Routes of Exposure

Exposure to hydrogen fluoride and its aqueous solution can occur through inhalation, ingestion, and eye or skin contact [Sittig 1991, p. 909].

* Summary of toxicology

1. Effects on Animals: Hydrogen fluoride is a severe pulmonary irritant as a gas; as a liquid, it is corrosive to the skin and eyes. The 1-hour LC(50)s in rats, mice, and monkeys are 1,276 ppm, and 1,774 ppm, respectively [Sax and Lewis 1989]. Rats, rabbits, guinea pigs, and dogs experienced irritation of the conjunctivae, nasal tissues, and respiratory system after acute inhalation exposures at near-lethal levels. Pathological lesions were observed in the kidney and liver, and the severity of the lesions was dose related. The external nares and nasal vestibules were black, and, at dosages causing considerable mortality, those areas showed zones of mucosal and submucosal necrosis. The skin of animals exposed at lethal concentrations showed superficial subcutaneous and deep dermal zones of acute inflammation. The hair of these animals could be pulled out with ease and skin ruptured under minimal tension [Clayton and Clayton 1982]. Experiments in which a 20-percent aqueous solution was instilled into the eyes of rabbits caused immediate damage in the form of total corneal opacification and conjunctival ischemia; within an hour, corneal stroma edema occurred, followed by necrosis of anterior ocular structures [Grant 1986]. Subacute, 30-day exposures at 30 ppm caused moderate hemorrhage and edema of the lungs in dogs, rabbits, and rats. At autopsy, rats showed renal cortical degeneration and necrosis, and dogs had ulceration of the scrotum. Exposures at 5.5 ppm under the same conditions produced localized hemorrhage in the lung in one of five dogs, but no changes were observed in the rabbit or rat [Clayton and Clayton 1982]. Hydrogen fluoride has also produced reproductive, teratogenic, and mutagenic effects in experimental animals [NIOSH 1991].

2. Effects on Humans: In humans, inhalation of hydrogen fluoride gas may cause immediate or delayed-onset pulmonary edema after a 1-hour exposure [Hathaway et al. 1991]. In addition, exposure to high concentrations of the vapors of hydrofluoric acid characteristically results in ulcerative tracheobronchitis and hemorrhagic pulmonary edema; this local reaction is equivalent to that caused by gaseous hydrogen chloride [Gosselin 1984]. From accidental, occupational, and volunteer exposures, it is estimated that the lowest lethal concentration for a 5-minute human exposure to hydrogen fluoride is in the range of 50 to 250 ppm [Hathaway et al. 1991]. Significant exposures by dermal or inhalation route may cause hypocalcemia and hypomagnesemia; cardiac arrhythmias may follow. Acute renal failure has also been documented after an ultimately fatal inhalation exposure [Hathaway et al. 1991]. Repeated exposure to excessive concentrations of fluoride over a period of years results in increased density of bone and eventually may cause crippling fluorosis (osteosclerosis caused by the deposition of fluoride in bone) [Hathaway et al. 1991]. Percutaneous absorption of pure liquefied hydrogen fluoride gas (chilled and under pressure until the vessel burst) produced severe hypocalcemia, multiple attacks of ventricular fibrillation, and death 9.5 hours after exposure. Skin contact with hydrogen fluoride or solutions containing more than 30 percent hydrogen fluoride produces immediate pain; reactions to more dilute solutions may be delayed for many hours. The accompanying pain is excruciating and persistent, and healing is delayed [Gosselin 1984]. Severe eye injuries may occur from splashes. Liquefied hydrogen fluoride gas has been known to destroy the eye and to require enucleation; the severity of burns from the aqueous solution depends on the concentration [Grant 1986]. Ingestion of an estimated 1.5 grams of hydrofluoric acid produces sudden death; however, repeated ingestion of small amounts of hydrogen fluoride may cause fluoride osteosclerosis [Gosselin 1984].

* Signs and symptoms of exposure

1. Acute exposure: Acute inhalation exposures produce severe eye, nose, and throat irritation; delayed fever, cyanosis, and pulmonary edema; and may cause death. Contact of the skin with the liquid may cause severe burns, erythema, and swelling, vesiculation, and serious crusting. With more serious burns, ulceration, blue-gray discoloration, and necrosis may occur [Hathaway et al. 1991]. Ingestion causes destruction of the tissues of the digestive tract and severe irritation of the respiratory tract [NLM 1992].

2. Chronic exposure: Chronic exposure to low airborne concentrations may cause nasal congestion and bronchitis. Repeated exposure to excessive hydrogen fluoride concentrations causes fluorosis; the early signs of increased bone density from fluoride deposition are most apparent in the lumbar spine and pelvis and can be detected by roentgenograph [NLM 1992].

EMERGENCY MEDICAL PROCEDURES

* Emergency medical procedures: [NIOSH to supply]

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, the location and proper use of emergency equipment, and methods of protecting themselves during rescue operations.

EXPOSURE SOURCES AND CONTROL METHODS

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

* The manufacture and transportation of hydrogen fluoride

* Use in manufacture of chlorofluorohydrocarbons for application as refrigerant fluids, aerosol propellants, specialty solvents, high-performance plastics, and foaming agents

* Use (as aqueous acid) in cleaning sandstone and marble, as a pickling agent for stainless steel and other metals, and as a cleaner in the meat packing industry

* Use (as anhydrous acid) in manufacture of aluminum fluoride and synthetic cryolite to reduce aluminum oxide to aluminum

* Use (as aqueous acid) in electroplating operations

* Liberated during manufacture of fertilizer and the burning of coal

* Use (as anhydrous acid) as a catalyst in alkylation of petroleum fractions to produce high-octane fuels

* Use (as aqueous acid) in etching, frosting, and polishing of glassware and ceramics

* Use as an acidizing agent during injection of acid into oil wells

* Used (as aqueous acid) in removal of sand and scale from foundry castings

* Use (as anhydrous acid) in separation and purification of uranium isotopes

* Use (as aqueous acid) in treating textiles to remove trace metals and in preparation of microelectronic circuits and quartz crystals for radio oscillators

* Use (as anhydrous acid) in production of fluorosilicone products

* Use (as anhydrous acid) in manufacture of pharmaceuticals and special dyes

* Use to arrest fermentation in brewing and for etching silicon wafers in semi-conductor manufacture, for purification of filter paper and graphite, in enamelling and galvanizing iron, and to increase the porosity of ceramics

Methods that are effective in controlling worker exposures to hydrogen fluoride, depending on the feasibility of implementation, are as follows:

* Process enclosure

* Local exhaust ventilation

* General dilution ventilation

* Personal protective equipment

Workers responding to a release or potential release of a hazardous substance must be protected as required by paragraph (q) of OSHA's Hazardous Waste Operations and Emergency Response Standard [29 CFR 1910.120].

Good sources of information about control methods are as follows:

1. ACGIH [1992]. Industrial ventilation--a manual of recommended practice. 21st ed. 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 SURVEILLANCE

OSHA is currently developing requirements for medical surveillance. When these requirements are promulgated, readers should refer to them for additional information and to determine whether employers whose employees are exposed to hydrogen fluoride are required to implement medical surveillance procedures.

* Medical Screening

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, 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 surveillance program is intended to supplement, not replace, such measures. To detect and control work-related health effects, medical evaluations should be performed (1) before job placement, (2) periodically during the term 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 hydrogen fluoride, a licensed health care professional 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, eyes, liver, kidneys, and respiratory system. Medical surveillance for respiratory disease should be conducted using the principles and methods recommended by the American Thoracic Society.

A preplacement medical evaluation is recommended to assess medical conditions that may be aggravated or may result in increased risk when a worker is exposed to hydrogen fluoride at or below the prescribed exposure limit. The health care professional 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, eyes, liver, kidneys, and respiratory system.

* Periodic medical evaluations

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 hydrogen fluoride exposure. The interviews, examinations, and medical screening tests should focus on identifying the adverse effects of hydrogen fluoride on the skin, eyes, liver, kidneys, or respiratory 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.

* Termination medical evaluations

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.

* Biological monitoring

Biological monitoring involves sampling and analyzing body tissues or fluids to provide an index of exposure to a toxic substance or metabolite. The fluoride concentration in urine is a useful index for exposure to hydrogen fluoride and has been found to average about 4 mg/liter in an end-of-shift specimen following an 8-hour exposure to 3 ppm hydrogen fluoride. Analysis of the specimens is conducted by direct measurement of inorganic fluoride using a fluoride-specific electrode.

WORKPLACE MONITORING AND MEASUREMENT

Determination of a worker's exposure to airborne hydrogen fluoride is made using a mixed cellulose ester filter (MCEF) 0.8 microns, a filter spacer, and a Na(2)CO(3) impregnated back-up pad in a three piece filter cassette. Samples are collected at a maximum flow rate of 1.5 liters/minute (TWA or STEL) until a maximum collection volume of 90 liters is reached. Analysis is conducted by using an ion-specific electrode (ISE). This method (OSHA ID 110) is partially validated and is described in the OSHA Computerized Information System [OSHA 1994] and in NIOSH Method No. 7903 (inorganic acids) [NIOSH 1994b].

PERSONAL HYGIENE PROCEDURES

If hydrogen fluoride contacts the skin, workers should flush the affected areas immediately with plenty of water, followed by washing with soap and water.

Clothing contaminated with hydrogen fluoride 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 hydrogen fluoride, particularly its potential for causing irritation.

A worker who handles hydrogen fluoride should thoroughly wash hands, forearms, and face with soap and water before eating, using tobacco products, using toilet facilities, applying cosmetics, or taking medication.

Workers should not eat, drink, use tobacco products, apply cosmetics, or take medication in areas where hydrogen fluoride or a solution containing hydrogen fluoride is handled, processed, or stored.

STORAGE

Hydrogen fluoride should be stored in a cool, dry, well-ventilated area in tightly sealed containers that are labeled in accordance with OSHA's Hazard Communication Standard [29 CFR 1910.1200]. Containers of hydrogen fluoride should be protected from physical damage and should be stored separately from metals, concrete, glass, strong bases, sodium hydroxide, potassium hydroxide, and ceramics.

SPILLS AND LEAKS

In the event of a spill or leak involving hydrogen fluoride, 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. Notify safety personnel.

2. Remove all sources of heat and ignition.

3. Ventilate the area of the spill or leak.

4. If source of leak is a cylinder and the leak cannot be stopped in place, remove the leaking cylinder to a safe place in the open air, and repair leak or allow cylinder to empty.

5. If in the liquid form, allow to vaporize and disperse the gas, or cover with sodium carbonate or an equal mixture of soda ash and slaked lime. After mixing, add water, if necessary, to form a slurry.

SPECIAL REQUIREMENTS

U.S. Environmental Protection Agency (EPA) requirements for emergency planning, reportable quantities of hazardous releases, community right-to-know, and hazardous waste management may change over time. Users are therefore advised to determine periodically whether new information is available.

* Emergency planning requirements

Employers owning or operating a facility at which there are 100 pounds or more of hydrogen fluoride must comply with EPA's emergency planning requirements [40 CFR Part 355.30].

* Reportable quantity requirements for hazardous releases

A hazardous substance release is defined by EPA as any spilling, leaking, pumping, pouring, emitting, emptying, discharging, injecting, escaping, leaching, dumping, or disposing into the environment (including the abandonment or discarding of contaminated containers) of hazardous substances. In the event of a release that is above the reportable quantity for that chemical, employers are required to notify the proper Federal, State, and local authorities [40 CFR 355.40].

The reportable quantity of hydrogen fluoride is 100 pounds. If an amount equal to or greater than this quantity is released within a 24-hour period in a manner that will expose persons outside the facility, employers are required to do the following: - Notify the National Response Center immediately at (800) 424-8802 or at (202) 426-2675 in Washington, D.C. [40 CFR 302.6].

- Notify the emergency response commission of the State likely to be affected by the release [40 CFR 355.40].

- Notify the community emergency coordinator to the local emergency planning committee (or relevant local emergency response personnel) of any area likely to be affected by the release [40 CFR 355.40].

* Community right-to-know requirements

Employers who own or operate facilities in SIC codes 20 to 39 that employ 10 or more workers and that manufacture 25,000 pounds or more of hydrogen fluoride per calendar year or otherwise use 10,000 pounds or more of hydrogen fluoride per calendar year are required by EPA [40 CFR Part 372.30] to submit a Toxic Chemical Release Inventory form (Form R) to EPA reporting the amount of hydrogen fluoride 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) [40 USC 6901 et seq.], EPA has specifically listed many chemical wastes as hazardous. Hydrogen fluoride is listed as a hazardous waste under RCRA and has been assigned EPA Hazardous Waste No. U134. This substance has been banned from land disposal until treated by venting compressed gases into an absorbing or reacting media, followed by neutralization.

Providing detailed information about the removal and disposal of specific chemicals is beyond the scope of this guideline. The U.S. Department of Transportation, EPA, 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 (703) 412-9810 (in the Washington, D.C. area) 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 hydrogen fluoride 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 emergencies. Workers should only use respirators 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 [29 CFR 1910.134]. Such a program must include respirator selection, an evaluation of the worker's ability to perform the work while wearing a respirator, the regular training of personnel, respirator 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 latest edition of the NIOSH Respirator Decision Logic [NIOSH 1987b] and the NIOSH Guide to Industrial Respiratory Protection [NIOSH 1987a].

PERSONAL PROTECTIVE EQUIPMENT

Workers should use appropriate personal protective clothing and equipment that must be carefully selected, used, and maintained to be effective in preventing skin contact with hydrogen fluoride. The selection of the appropriate personal protective equipment (PPE) (e.g., gloves, sleeves, encapsulating suits) should be based on the extent of the worker's potential exposure to hydrogen fluoride. The resistance of various materials to permeation by 30 to 70 percent solutions of hydrogen fluoride is shown below:

(*) Not recommended, degradation may occur

To evaluate the use of these PPE materials with hydrogen fluoride, users should consult the best available performance data and manufacturers' recommendations. Significant differences have been demonstrated in the chemical resistance of generically similar PPE materials (e.g., butyl) produced by different manufacturers. In addition, the chemical resistance of a mixture may be significantly different from that of any of its neat components.

Any chemical-resistant clothing that is used should be periodically evaluated to determine its effectiveness in preventing dermal contact. Safety showers and eye wash stations should be located close to operations that involve hydrogen fluoride.

Splash-proof chemical safety goggles or face shields (20 to 30 cm long, minimum) should be worn during any operation in which a solvent, caustic, or other toxic substance may be splashed into the eyes.

In addition to the possible need for wearing protective outer apparel (e.g., aprons, encapsulating suits), workers should wear work uniforms, coveralls, or similar full-body coverings that are laundered each day. Employers should provide lockers or other closed areas to store work and street clothing separately. Employers should collect work clothing at the end of each work shift and provide for its laundering. Laundry personnel should be informed about the potential hazards of handling contaminated clothing and instructed about measures to minimize their health risk.

Protective clothing should be kept free of oil and grease and should be inspected and maintained regularly to preserve its effectiveness.

Protective clothing may interfere with the body's heat dissipation, especially during hot weather or during work in hot or poorly ventilated work environments.

REFERENCES

ACGIH [1991]. Documentation of the threshold limit values and biological exposure indices. 6th ed. Cincinnati, OH: American Conference of Governmental Industrial Hygienists.

ACGIH [1994]. 1994-1995 Threshold limit values for chemical substances and physical agents and biological exposure indices. Cincinnati, OH: American Conference of Governmental Industrial Hygienists.

Amoore JE, Hautala E [1983]. Odor as an aid to chemical safety: odor thresholds compared with threshold limit values and volatilities for 214 industrial chemicals in air and water dilution. J of App Tox 3(6):272-290.

ATS [1987]. Standardization of spirometry -- 1987 update. American Thoracic Society. Am Rev Respir Dis 136:1285-1296.

CFR. Code of Federal regulations. Washington, DC: U.S. Government Printing Office, Office of the Federal Register.

Clayton G, Clayton F [1981-1982]. Patty's industrial hygiene and toxicology. 3rd rev. ed. New York, NY: John Wiley & Sons.

DOT [1993]. 1993 Emergency response guidebook, guides 15, 59. Washington, DC: U.S. Department of Transportation, Office of Hazardous Materials Transportation, Research and Special Programs Administration.

Forsberg K, Mansdorf SZ [1993]. Quick selection guide to chemical protective clothing. New York, NY: Van Nostrand Reinhold.

Genium [1987]. Material safety data sheet No. 6. Schenectady, NY: Genium Publishing Corporation.

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

Grant WM [1986]. Toxicology of the eye. 3rd ed. Springfield, IL: Charles C Thomas.

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

Lide DR [1993]. CRC handbook of chemistry and physics. 73rd ed. Boca Raton, FL: CRC Press, Inc.

Mickelsen RL, Hall RC [1987]. A breakthrough time comparison of nitrile and neoprene glove materials produced by different glove manufacturers. Am Ind Hyg Assoc J 48(11): 941-947.

Mickelsen RL, Hall RC, Chern RT, Myers JR [1991]. Evaluation of a simple weight-loss method for determining the permeation of organic liquids through rubber films. Am Ind Hyg Assoc J 52(10): 445-447.

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

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 [1987b]. NIOSH 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 [1991]. Registry of toxic effects of chemical substances: Hydrogen Fluoride. Cincinnati, OH: U.S. Department of Health and Human Services, Public Health Service, Centers for Disease Control, National Institute for Occupational Safety and Health, Division of Standards Development and Technology Transfer, Technical Information Branch.

NIOSH [1992]. Recommendations for occupational safety and health: Compendium of policy documents and 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, DHHS (NIOSH) Publication No. 92-100.

NIOSH [1994a]. NIOSH pocket guide to chemical hazards. 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. 94-116.

NIOSH [1994b]. NIOSH manual of analytical methods. 4th ed. 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. 94-113.

NJDH [1992]. Hazardous substance fact sheet: Hydrogen Fluoride. Trenton, NJ: New Jersey Department of Health.

NLM [1992]. Hazardous substances data bank: Hydrogen Fluoride. Bethesda, MD: National Library of Medicine.

OSHA [1994]. Computerized information system. Washington, DC: U.S. Department of Labor, Occupational Safety and Health Administration.

Parmeggiani L [1983]. Encyclopedia of occupational health and safety. 3rd rev. ed. Geneva, Switzerland: International Labour Organisation.

Rom WN [1983]. Environmental and occupational medicine. First ed. Boston, MA: Little, Brown and Company.

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

Sittig M [1991]. Handbook of toxic and hazardous chemicals. 3rd ed. Park Ridge, NJ: Noyes Publications.

USC. United States code. Washington. DC: U.S. Government Printing Office.

Windholz M, ed. [1983]. Windholz Index 10th ed. Rahway, NJ: Windholz & Company.