Hydrogen sulfide, safety

Z390.1 Accepted Practices for Hydrogen Sulfide Safety Training Programs... 

Hydrochloric acid can be used to dissolve calcium carbonate and iron sulfide scales. However, iron sulfide chemically reacts with hydrochloric acid and produces hydrogen sulfide, a highly toxic gas having the odor of rotten eggs. Due to the high toxicity of hydrogen sulfide, safety provisions need to be implemented. 

The precipitated acetyHde must be decomposed with hydrochloric acid after the titration as a safety measure. Concentrated solutions of silver nitrate or silver perchlorate form soluble complexes of silver acetyHde (89). Ammonia and hydrogen sulfide interfere with the silver nitrate method which is less... 

Hydrogen Sulfide, Product Safety Information Sheet, Stauffer Chemical Co., Industrial Chemical Division, Westport, Coim., 1973. 

NIOSH. 1977a. Criteria for a recommended standard Occupational exposure to hydrogen sulfide. Cincinnati, OH U.S. Department of Health and Human Services, Public Health Service, National Institute for Occupational Safety and Health. NIOSH-77-158. NTIS publication no. PB-274196. 

NIOSH. 1991. Fatal accident circumstances and epidemiology (FACE) report Two maintenance workers die after inhaling hydrogen sulfide in manhole, January 31, 1989. National Institute for Occupational Safety and Health. Morgantown, WV. NTIS publication no. PB91212761. 

National Institute for Occupational Safety and Health Criteria for a Recommended Standard... Occupational Exposure to Hydrogen Sulfide. DHEW (NIOSH), pp 22-64. Washington, DC, US Government Printing Office, 1977... 

Caution. This synthesis should be carried out in a well-ventilated hood because of the use of highly poisonous hydrogen sulfide. Usual safety measures recommended for handling cyanide salts should be carefully observed during the synthesis and the disposal of the residues. Exposure of any of those products to acids could result in liberation of highly poisonous hydrogen cyanide. 

TLV The TLV or Threshold Limit Value refers to a safe level of exposure by inhalation. The definition was established by the American Conference of Governmental Hygienists. There are several variations or criteria levels for the TLV. As an example, hydrogen sulfide has a TLV for short-term exposure limits (STEL) of 15 minutes of only 5 ppm. Comparing this to the TLV-STEL of 400 ppm for carbon monoxide provides an indication of the need to be extremely careful when H2S is suspected. Under OSHA Standards, and particularly on MSDS (Material Safety Data Sheets) compounds are associated with a time weighted average (TWA) TLV, which is the allowable concentration for an 8-hour continuous exposure period. For firefighting purposes, the short-term exposure is likely more realistic. 

Health and Safety Factors. Carbonyl sulfide is dangerously poisonous, more so because it is practically ododess when pure. It is lethal to rats at 2900 ppm. Studies show an LD5Q (rat, ip) of 22.5 mg/kg. The mechanism of toxic action appears to involve breakdown to hydrogen sulfide (36). It acts principally on the central nervous system with death resulting mainly from respiratory paralysis. Litde is known regarding the health effects of subacute or chronic exposure to carbonyl sulfide a 400- Jg/m3 max level has been suggested until more data are available (37). Carbon oxysulfide has a reported inhalation toxicity in mice LD5Q (mouse) = 2900 ppm (37). 

Occupational Exposure to Hydrogen Sulfide, Criteria Document, Dept, of Health, Education, and Welfare (NIOSH) Publication No. 77-158 National Technical Information Service Publication No. PB274196, National Institute of Occupational Safety and Health, Washington, D.C., May 1977. 

The Texas Air Control Board was responsible for monitoring emissions of hydrogen sulfide and sulfur dioxide during all phases of the Sulphlex construction The measurements indicated that neither gas was present at levels near those which would pose a safety or environmental hazard during any phase of the operation. 

U.S. Chemical Safety and Hazard Investigation Board, Investigation Report—Hydrogen Sulfide Poisoning. U.S. Chemical Safety and Hazard Investigation Board Report No. 2002-01-I-AL, Jan. 2003. 

One safety trick is to add to your total HF solution about one or two percent nitric acid. This addition will not assist the cleaning properties to any significant amount, but it will add more effective warning characteristics to both the odor and any accidental skin contact. This practice is similar in concept to the addition of hydrogen sulfide to methane. 

The US Occupational Safety and Health Administration (OSHA) permissible exposure limits for hydrogen sulfide is 10 ppm (time weighted average) for an eight-hour exposure and 15 ppm (shortterm exposure limit). The transitional limits are 20 ppm (ceiling) and 50 ppm (peak - ten-minute exposure). 

SAFETY PROFILE Poison by intravenous and intraperitoneal routes. An allergen can cause contact dermatitis. Emits hydrogen sulfide. See also SULFIDES. When heated to decomposition it emits very toxic NOx, SOx, and NH3. 

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