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 This information may be superseded by new developments in the field of industrial hygiene.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 CHLORIDE

INTRODUCTION

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 Recommendations may be superseded by new developments in these fields; readers are therefore advised to regard these recommendations as general guidelines and to determine whether new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

HCl

* Structure

(For Structure, see paper copy)

* Synonyms

Anhydrous hydrochloric acid, hydrochloride, muriatic acid, spirits of salt, hydrochloric acid, chlorohydric acid, emulsion bowl cleaner

* Identifiers

1. CAS No.: 7647-01-0

2. RTECS No.: MW4025000

3. DOT UN: 1050 15

4. DOT label: Poison gas, corrosive

* Appearance and odor

Hydrogen chloride is a colorless to slightly, yellow gas with an irritating, pungent odor. The air odor threshold concentration for hydrogen chloride has been reported as 0.77 part per million (ppm) parts of air.

CHEMICAL AND PHYSICAL PROPERTIES

* Physical data

1. Molecular weight: 36.46

2. Boiling point (at 760 mm Hg): -85.05 degrees C (-121.09 degrees F)

3. Specific gravity: 1.187 at -84.9 degrees C (-120.82 degrees F)

4. Vapor density: 1.268

5. Melting point: -114.2 degrees C (-173.6 degrees F)

6. Vapor pressure at 20 degrees C (68 degrees F): Greater than 1 mm Hg

7. Solubility: Soluble in water, alcohol, benzene, and ether.

8. Evaporation rate: Data not available.

* Reactivity

1. Conditions contributing to instability: None reported.

2. Incompatibilities: Contact between hydrogen chloride and hydroxides, amines, alkalis, or metals, such as copper, brass, zinc, potassium, and sodium should be avoided.

3. Hazardous decomposition products: Toxic gases and vapors such as chlorine may be released in a fire involving hydrochloric acid.

4. Special precautions: None reported.

* Flammability

Hydrogen chloride is a nonflammable gas.

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

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. Use water spray, fog, or regular foam to fight large fires involving hydrogen chloride.

Fires involving hydrogen chloride should be fought upwind from the maximum distance possible. Keep unnecessary people away; isolate the hazard area and deny entry. Isolate the leak or spill 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 chloride 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 chloride.

EXPOSURE LIMITS

* OSHA PEL

The current Occupational Safety and Health Administration (OSHA) permissible exposure limit(s) (PEL[s]) for hydrogen chloride is 5 ppm (7 milligrams per cubic meter (mg/m(3))) as a ceiling limit. A worker's exposure to hydrogen chloride shall at no time exceed this ceiling level [29 CFR 1910.1000, Table Z-1].

* NIOSH REL

The National Institute for Occupational Safety and Health (NIOSH) has established a recommended exposure limit (REL) for hydrogen chloride of 5 ppm (7 mg/m(3)) as a ceiling [NIOSH 1992].

* ACGIH TLV

The American Conference of Governmental Industrial Hygienists (ACGIH) has assigned hydrogen chloride a ceiling limit value of 5 ppm (7.5 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 eye, mucous membrane, and skin irritation [NIOSH 1992].

The ACGIH limit is based on the risk of acute irritation [ACGIH 1991, p. 773].

HEALTH HAZARD INFORMATION

* Routes of Exposure

Exposure to hydrogen chloride can occur through inhalation, ingestion, and eye or skin contact [Sittig 1991].

* Summary of toxicology

1. Effects on Animals: Hydrogen chloride is a severe irritant of the eyes and respiratory system. The 30-minute LC(50)s in rats and mice and 4,701 ppm and 2,644, respectively [Sax and Lewis 1989]. Animals exposed to high concentrations of hydrogen chloride gas developed necrosis of the tracheal and bronchial epithelium; pulmonary edema, atelectasis, and emphysema; and damage to the pulmonary blood vessels and liver [ACGIH 1991]. Chronic exposure to 10 ppm for 6 hours/day for life did not cause neoplastic lesions or serious irritant effects in the nasal epithelium of rats [Hathaway et al. 1991]. In experimental animals, exposure to a concentration of 1,350 ppm hydrogen chloride gas caused clouding of the cornea after 1.5 hours and exposure to 3,000 ppm for 6 hours caused slight erosion of the corneal epithelium. Exposure to 100 ppm for 6 hours daily for 50 days caused only slight irritation of the eyes, but no permanent injury [Grant 1986]. Hydrochloric acid is mildly toxic by ingestion; the oral LD(50) in rabbits is 900 mg/kg [Sax and Lewis 1989]. Hydrochloric acid is injurious to the rabbit eye only at concentrations having an acidity below pH 3. Contact of the eye with 0.25N to 1N acid for 20 seconds resulted in some scarring of rabbit corneas; in rare instances, opacities of the lens have been produced by splashes of the acid [Grant 1986]. Hydrochloric acid has produced mutagenic effects in bacterial and insect test systems [NIOSH 1995].

2. Effects on Humans: Hydrogen chloride is irritating and corrosive to the eyes, skin, and mucous membranes. Exposure to high concentrations can cause laryngitis, bronchitis, and pulmonary edema [Rom 1983]. Brief exposures (up to a few minutes) to concentrations in the range of 1,300 to 2,000 ppm are lethal to humans [Braker and Mossman 1980]. In workers, exposure to 50 to 100 ppm for 1 hour was barely tolerable; short exposure to 35 ppm caused irritation of the throat, and 10 ppm was considered the maximal concentration allowable for prolonged exposure. In one study, workers chronically exposed to hydrogen chloride did not exhibit the pulmonary function changes observed in nine subjects exposed to similar concentrations, which suggests that workers become acclimatized to hydrogen chloride [Hathaway et al. 1991]. Dental discoloration and erosion of exposed incisors may occur on prolonged exposure to low concentrations [Sittig 1991]. Hydrochloric acid causes burns of the skin and mucous membranes; the severity of the burns depends on the concentration of the solution. Burns may progress to ulcerations and lead to keloid and retractile scarring. Frequent contact of the skin with aqueous solution may cause dermatitis. Contact of the eyes with aqueous solutions may produce reduced vision or blindness [Parmeggiani 1983]. Ingestion of hydrochloric acid causes severe burns of the mouth, esophagus, and stomach, with consequent pain, nausea, and vomiting [Hathaway et al. 1991].

* Signs and symptoms of exposure

1. Acute exposure: Acute exposure to hydrogen chloride vapor or aerosol produces inflammation and may cause ulceration of the nose, throat, and larynx; laryngeal spasm or pulmonary edema may occur on rare occasions. Eye and skin burns occur at high concentrations. Burns of the skin and mucous membranes result from contact with the solution [NLM 1995; Parmeggiani 1983]. Frostbite may occur from contact with the cryogenic liquid [Sax and Lewis 1989]. Both the gas and solutions of hydrogen chloride may cause eye irritation, severe burns, and permanent damage with loss of sight [Windholz 1983]. Ingestion causes corrosion of the mucous membranes, esophagus, and stomach; dysphagia; nausea; vomiting; intense thirst; and diarrhea. Circulatory collapse and death may follow [Windholz 1983].

2. Chronic exposure: Chronic exposure by skin contact with aqueous solutions may result in dermatitis and photosensitization [Parmeggiani 1983]. Dental discoloration and erosion of exposed incisors may occur on prolonged exposure to low concentrations of hydrogen chloride [Hathaway et al. 1991].

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 chloride and lead to worker exposures to this substance:

* The manufacture and transportation of hydrogen chloride

* Use during pickling of metals including stainless steel, iron, nickel, and monel

* Use as a catalyst or chlorinating agent in chemical synthesis; during metal treatment and fabricating operations in electroplating, acid dipping, stripping, electropolishing, etching, welding, and flamecutting of metal primed with paint or cleaned with chlorinated hydrocarbons; as a gaseous flux in babbitting

* Use in oxyhydrochlorination processing in production of chlorinated hydrocarbons

* Use to refine edible oils and fats and in manufacture of sugar cane refining, glucose, corn sugar, and in brewing and other food processing operations

* Use in industrial chemical cleaning operations; in production of plastics and resins

* Use in rubber manufacture including synthesis of chloroprene; as a chlorinating agent and in coagulation of latex

* Liberated during synthesis of pharmaceutical hydrochlorides, vinyl chloride, alkyl chlorides, arsenious chloride, phosphoric acid, gelatin, sodium glutamate, ammonium chloride, chloride dioxide; used in extraction and reduction processing of metal ores

* Use as a deliner of hides and in leather tanning

* Use in activation of petroleum wells; in waste treatment operations for neutralization of alkaline waste streams; in production of chlorine

* Use in manufacture of fertilizers, dyes, dyestuffs, artificial silk, and pigments for paints

* Use in petroleum refining, soap refining, and the photographic industry, and in the textile industry to separate cotton from wool and to delint cotton

* Use in removing scale from boilers and heat-exchange equipment, as a laboratory reagent, an alcohol denaturant, and a veterinary antiseptic

Methods that are effective in controlling worker exposures to hydrogen chloride, 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 chloride 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 chloride, 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 eyes, skin, 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 chloride 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 eyes, skin, 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 chloride exposure. The interviews, examinations, and medical screening tests should focus on identifying the adverse effects of hydrogen chloride on the eyes, skin, and 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. No biological monitoring test acceptable for routine use has yet been developed for hydrogen chloride.

WORKPLACE MONITORING AND MEASUREMENT

Determination of a worker's exposure to airborne hydrogen chloride is made using a treated silica gel tube. Samples are collected at a maximum flow rate of 0.5 liter/minute (ceiling) until a minimum collection volume of 2.5 liters is reached. Analysis is conducted by ion chromatography. This method 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 chloride 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 chloride 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 chloride, particularly its potential for causing irritation.

A worker who handles hydrogen chloride 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 chloride or a solution containing hydrogen chloride is handled, processed, or stored.

STORAGE

Hydrogen chloride 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 chloride should be protected from physical damage and should be stored separately from hydroxides, amines, alkalis, or metals, such as copper, brass, zinc, potassium, and sodium.

SPILLS AND LEAKS

In the event of a spill or leak involving hydrogen chloride, 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. Stop leak if this can be done without risk. If the 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. All spills on land involving liquid hydrogen chloride or hydrochloric acid should be contained, if possible, to prevent entry into bodies of water or sewer systems. Vapors can be dispersed with water fog or spray. Do not put water directly on leak or spill area.

6. Neutralize spills with crushed limestone, soda ash, lime, or sodium bicarbonate. After neutralizing, take up with sand or other noncombustible absorbent material and place into closed containers for later disposal.

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

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 500 pounds or more of hydrogen chloride (gas only) 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 chloride is 5,000 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 chloride per calendar year or otherwise use 10,000 pounds or more of hydrogen chloride 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 chloride 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. Although hydrogen chloride is not specifically listed as a hazardous waste under RCRA, EPA requires employers to treat waste as hazardous if it exhibits any of the characteristics discussed above.

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 chloride 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 chloride. 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 chloride. The resistance of various materials to permeation by hydrogen chloride is shown below:

(*) Not recommended, degradation may occur

To evaluate the use of these PPE materials with hydrogen chloride, 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 chloride.

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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