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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 Recommendations may be superseded by new developments in these fields; readers are therefore advised to regard these recommendations as general guidelines and to determine whether new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
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
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.
Hydrogen fluoride is a nonflammable gas . The National Fire Protection Association has assigned a flammability rating of 0 (minimal fire hazard) to hydrogen fluoride.
* 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
* Emergency medical procedures: [NIOSH to supply] 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:
Good sources of information about control methods are as follows:
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:
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.
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