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 This information may be superseded by new developments in the field of industrial hygiene.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

INTRODUCTION

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 Recommendations may be superseded by new developments in these fields; readers are therefore advised to regard these recommendations as general guidelines and to determine whether new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

HCN

* Structure

(For Structure, see paper copy)

* Synonyms

Hydrocyanic acid, prussic acid, formonitrile, formic anammonide, carbon hydride nitride, cyclon

* Identifiers

1. CAS No.: 74-90-8

2. RTECS No.: MW6825000

3. DOT UN: 1613 55 (aqueous solution, less than 20 percent); 1614 57 (anhydrous, stabilized (absorbed); 1051 13 (anhydrous, stabilized)

4. DOT label: Poison (1614); Poison, flammable liquid (1051); None (1613)

* Appearance and odor

Hydrogen cyanide is a colorless gas or bluish-white liquid with a bitter almond odor. An air odor threshold concentration for hydrogen cyanide of 0.58 part per million (ppm) parts of air has been reported.

CHEMICAL AND PHYSICAL PROPERTIES

* Physical data

1. Molecular weight: 27.03

2. Boiling point (at 760 mm Hg): 26 degrees C (79 degrees F)

3. Specific gravity: 0.7 at 20 degrees C (68 degrees F)

4. Vapor density: 0.94

5. Melting point: -13.4 degrees C (7.88 degrees F)

6. Vapor pressure at 20 degrees C (68 degrees F): 620 mm Hg

7. Solubility: Miscible with water and alcohol, and slightly soluble in ether.

8. Evaporation rate: Data not available.

* Reactivity

1. Conditions contributing to instability: Explosive hazards can occur on exposure to air, sources of ignition, including heat (polymerizes explosively at 50-60degreesC), or open flame; and when stored for long periods of time.

2. Incompatibilities: Contact between hydrogen cyanide and amines; oxidizers such as perchlorates, peroxides, permanganates, chlorates, and nitrates; strong acids such as hydrochloric, sulfuric and nitric; sodium hydroxide, calcium hydroxide, sodium carbonate, water, ammonia, acetaldehyde, and caustics should be avoided.

3. Hazardous decomposition products: Toxic gases such as cyanide may be released in a fire involving hydrogen cyanide.

4. Special precautions: None reported.

* Flammability

The National Fire Protection Association has assigned a flammability rating of 4 (severe fire hazard) to hydrogen cyanide.

1. Flash point: -17.78 degrees C (0 degrees F) (closed cup)

2. Autoignition temperature: 538 degrees C (1000 degrees F)

3. Flammable limits in air (percent by volume): Lower, 5.6 percent; upper, 40.0 percent

4. Extinguishant: For small fires use dry chemical, water spray, or regular foam; and let fire burn unless the leak can be stopped immediately. Use water spray, fog, or regular foam to fight large fires involving hydrogen cyanide.

Fires involving hydrogen cyanide should be fought upwind from the maximum distance possible. Keep unnecessary people away; isolate the hazard area and deny entry. Isolate the area for 1/2 mile in all directions if a tank, rail car, or tank truck is involved in the fire. 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. Vapors may travel to a source of ignition and flash back. Vapors are an explosion and poison hazard indoors, outdoors, or in sewers. Containers of hydrogen cyanide 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. Stay away from the ends of containers. Dike fire control water for later disposal. Do not scatter the material. Firefighters should wear a full set of chemical protective clothing and self-contained breathing apparatus when fighting fires involving hydrogen cyanide.

EXPOSURE LIMITS

* OSHA PEL

The current Occupational Safety and Health Administration (OSHA) permissible exposure limit (PEL) for hydrogen cyanide is 10 ppm (11 milligrams per cubic meter (mg/m(3))) as an 8-hour time-weighted average (TWA) concentration. The OSHA PEL also bears a "Skin" notation, which indicates that the cutaneous route of exposure (including mucous membranes and eyes) contributes to overall exposure [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 cyanide of 4.7 ppm (5 mg/m(3)) as a STEL. NIOSH also assigns a "Skin" notation to hydrogen cyanide [NIOSH 1992].

* ACGIH TLV

The American Conference of Governmental Industrial Hygienists (ACGIH) has assigned hydrogen cyanide a ceiling limit value of 4.7 ppm (5 mg/m(3)), which should not be exceeded during any part of the working exposure. The ACGIH also assigns a "Skin" notation to hydrogen cyanide [ACGIH 1994, p. 23].

* Rationale for Limits

The NIOSH limit is based on the risk of thyroid, blood, and respiratory effects [NIOSH 1992].

The ACGIH limit is based on the risk of acute poisoning [ACGIH 1991, p. 776].

HEALTH HAZARD INFORMATION

* Routes of Exposure

Exposure to hydrogen cyanide can occur through inhalation, ingestion, eye or skin contact, and absorption through the skin, eyes, and mucous membranes [Sittig 1991; Rom 1992].

* Summary of toxicology

1. Effects on Animals: Cyanide is a potent and rapidly acting chemical asphyxiant; it prevents tissue utilization of oxygen by inhibiting the tissue enzyme cytochrome oxidase. The organs especially sensitive to cyanide damage are those whose function depends on an adequate supply of oxygen; i.e., the brain and heart [Gosselin 1984]. The 1-minute inhalation LC(50) in dogs is 616 mg/m(3); in rats and mice, the 5-minute inhalation LC(50) values are 484 ppm and 323 ppm, respectively [Sax and Lewis 1989]. The oral LD(50) in the mouse is 3.7 mg/kg [Sax and Lewis 1989]. Animals lethally or sublethally poisoned by cyanides have exhibited optic nerve and retinal damage. Repeated administration of cyanide caused central nervous system lesions involving degeneration of the myelin sheath in rats and monkeys [Grant 1986]. Animals acutely poisoned demonstrate cherry-red blood, agonal hemorrhages on the heart, and congestion and petechial hemorrhage of the lungs and gastrointestinal tract [NLM 1995]. Instilled into the conjunctival sac of the eyes of rabbits, hydrogen cyanide caused death within 3 to 12 minutes after instillation [NLM 1995].

2. Effects on Humans: Hydrogen cyanide can cause rapid death due to metabolic asphyxiation. Death can occur within seconds or minutes of the inhalation of high concentrations of hydrogen cyanide gas. A recent study reports an estimated LC(50) in humans of 3,404 ppm for a 1-minute exposure; other sources report that 270 ppm is fatal after 6 to 8 minutes, 181 ppm after 10 minutes and 135 ppm after 30 minutes [Hathaway et al. 1991]. Cyanide directly stimulates the chemoreceptors of the carotid and aortic bodies, causing hyperpnea. Cardiac irregularities are often noted [Amdur 1991]. Liquid hydrogen cyanide, hydrogen cyanide in aqueous solution [hydrocyanic acid], and the concentrated vapor are all absorbed rapidly through the intact skin and may cause systemic poisoning with little or no irritant effect on the skin itself. The liquid in contact with the eye may cause only local irritation; however, the attendant absorption may be hazardous [Hathaway et al. 1991]. Industrial exposure to hydrogen cyanide solutions has caused dermatitis, itching, scarlet rash, papules, and nose irritation and bleeding. Perforation of the nasal septum has also occurred [NLM 1995]. Workers exposed to hydrogen cyanide at concentrations ranging from 4 to 12 ppm for 7 years showed an increase in symptoms such as headaches, weakness, changes in taste and smell, irritation of the throat, vomiting, effort dyspnea, lacrimation, abdominal colic, precordial pain, and nervous instability [ACGIH 1991]. Workers exposed to low concentrations (not further specified) of hydrogen cyanide have developed enlarged thyroid glands [NLM 1995].

* Signs and symptoms of exposure

1. Acute exposure: Acute exposure to cyanide can result in symptoms including weakness, headache, confusion, vertigo, fatigue, anxiety, dyspnea, and occasionally nausea and vomiting. Respiratory rate and depth are usually increased initially and at later stages become slow and gasping. Coma and convulsions occur in some cases. If cyanosis is present, it usually indicates that respiration has either ceased or has been inadequate for a few minutes. If large amounts of cyanide have been absorbed, collapse is usually instantaneous; unconsciousness; often with convulsions, is followed almost immediately by death [Hathaway et al. 1991].

2. Chronic exposure: Chronic exposure to cyanide can result in symptoms similar to those reported after acute exposure, e.g., weakness, nausea, headache, and vertigo [Hathaway et al. 1991]. Dermatitis, itching, scarlet rash, papules, and severe nose irritation have also been reported [Parmeggiani 1983]. In addition, long-term exposures have produced thyroid changes, including frank goiter [Gosselin 1984]. Only occasionally has reference been made to eye irritation, conjunctivitis, or superficial keratitis developing after chronic exposure to hydrogen cyanide gas [Grant 1986].

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 cyanide and lead to worker exposures to this substance:

* The manufacture and transportation of hydrogen cyanide

* Use in fumigation of ships, structures, and agricultural crops and as a nematocide

* Liberated during use of cyanide salts or solutions in metal treatment operations, blast furnace and coke oven operations, metal ore processing, and photoengraving operations

* Use in production of intermediates in synthesis of resin monomers, acrylic plastics, acrylonitrile, Nylon 66, cyanide salts, lactic acid, nitrates, chelating agents, dyes, pharmaceuticals, and specialty chemicals

* Liberated during petroleum refining and electroplating

* Use in the manufacture of silver and metal polishes, and electroplating solutions, and as a reagent

* Use as the instrument of execution for convicted criminals in prison gas chambers in some states

Methods that are effective in controlling worker exposures to hydrogen cyanide, 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 cyanide 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 cyanide, 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 liver, kidneys, blood, cardiovascular system, and central nervous system.

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 cyanide 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 liver, kidneys, blood, cardiovascular system, and central nervous 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 cyanide exposure. The interviews, examinations, and medical screening tests should focus on identifying the adverse effects of hydrogen cyanide on the liver, kidneys, blood, cardiovascular system, and 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.

* 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 cyanide.

WORKPLACE MONITORING AND MEASUREMENT

Determination of a worker's exposure to airborne hydrogen cyanide is made using a mixed cellulose ester filter (MCEF) 0.8 microns in series with a midget fritted glass bubbler (MFGB) containing 10 mL 0.1 N NaOH. Samples are collected at a maximum flow rate of 1 liter/minute until a maximum collection volume of 120 liters is reached for TWA sampling or a recommended volume of 15 liters is reached for STEL sampling. Analysis is conducted by using an ion specific electrode (ISE). This method (OSHA ID - 120) is fully validated and is described in the OSHA Computerized Information System [OSHA 1994] and a similar method is described in NIOSH Method No. 7904 [NIOSH 1994b].

PERSONAL HYGIENE PROCEDURES

If hydrogen cyanide 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 cyanide 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 cyanide, particularly its potential for severe systemic toxicity by dermal absorption or inhalation.

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

STORAGE

Hydrogen cyanide 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 cyanide should be protected from physical damage and should be stored separately from amines; oxidizers such as perchlorates, peroxides, permanganates, chlorates, and nitrates; strong acids such as hydrochloric, sulfuric and nitric; sodium hydroxide, calcium hydroxide, sodium carbonate, water, ammonia, acetaldehyde, and caustics.

SPILLS AND LEAKS

In the event of a spill or leak involving hydrogen cyanide, 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 potentially explosive atmospheres.

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

5. Use non-sparking tools.

6. If source of leak is a cylinder and the leak cannot be stopped in place, remove the laking cylinder to a safe place and repair leak or allow cylinder to empty. Use water sprays to protect personnel attempting to locate and seal the source of escaping hydrogen cyanide gas.

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

8. Prevent hydrogen cyanide from accumulating in a confined space, such as a sewer, because of the possibility of an explosion.

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 cyanide 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 cyanide is 10 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 cyanide per calendar year or otherwise use 10,000 pounds or more of hydrogen cyanide 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 cyanide 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 cyanide is listed as a hazardous waste under RCRA and has been assigned EPA Hazardous Waste No. P063. It is approved for land disposal after treatment and only if the concentration of hydrogen cyanide in the waste or treatment residual does not exceed 110 mg/kg.

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

(*) Material estimated (but not tested) to provide 4 hours of protection
(**) Not recommended, degradation may occur

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

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.

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

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, guide 13, 55, 57. 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 [1989]. Material safety data sheet No. 686. 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.

Amdur MO, Doull J, Klaassen CD [1991]. Casarett and Doull's toxicology. 4th ed. New York, NY: McGraw-Hill, Inc.

Lewis RJ, ed. [1993]. Hawley's condensed chemical dictionary. 12th ed. New York, NY: Van Nostrand Reinhold Company.

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 [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.

NIOSH [1995]. Registry of toxic effects of chemical substances: Hydrogen Cyanide. 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.

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

NLM [1995]. Hazardous substances data bank: Hydrogen Cyanide. 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.

Patnaik P [1992]. A comprehensive guide to the hazardous properties of chemical substances. New York, NY: Van Nostrand Reinhold.

Rom WN [1992]. Environmental and occupational medicine. 2nd 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]. Merck Index 10th ed. Rahway, NJ: Merck & Company.