April 1960
Maximale Immissions-Konzentrationen
                         OF HYDROGEN SULPHIDE
      This publication, translated from the German, was prepared by
      the Subcommittee on Effects of Hydrogen Sulphide of the Committee
      on Effects of Dust and Gas of the VDI Committee on Air Purification.
      All rights reserved.
                    Reproduced with permission by the
                  0 0     Public Health Service
                            Washington, D. C.
                    VDI-Handbuch R'einhaltung der Luft


    This ia one of several dozen VDI Clean Air Committee specifications
on air purification which the Division of Air Pollution of the U.S. Public
Health Service has obtained permission to translate,  publish, and distri-
bute in limited quantity.  A complete list of the VDI publications being
published by the Division of Air  Pollution appears on the inside back
cover.  Because the VDI Committee from time to time revises these
specifications, this and  other publications in the  series may be super-
seded by later publications.

    The VDI Clean Air Committee specifications are compiled by trade
or professional associations and published by the Committee.  The Com-
mittee has neither official status nor regulatory authority,  although West
German governmental agencies participate in its activities.  Air quality
specifications published by the Committee are therefore advisory, rather
than regulatory.   They may however later be adopted by West German
governmental authorities.

    The English translations were done by the  Joint Publications Research
Service of the Office  of Technical Services, U.S. Department of Commerce.
It should be borne in  mind that various terms literally taken from the Ger-
man do not have the same connotation in English; for example, the word
"standard" frequently appears where the word "criteria" might better
reflect the comparable American meaning, since in this country "standard"
is generally meant to imply a legally enforceable value,  while  "criteria"
usually means a recommended value upon which standards may be based.

    The publication and distribution of these translations by the  Public
Health Service constitutes neither endorsement of the specifications nor
of the air quality or emission limitations recommended in them.  We
believe that they contain much useful information that would otherwise
not  be available to non-readers of German and  for this reason have made
them  available to workers in the air pollution field in the United  States.


                          OF HYDROGEN SULPHIDE
                              Prepared bys

              Subcommittee on Effects of Hydrogen Sulphide
              of the Committee on Effects of Dust  and Gas
                of the VDI Committee on Air Purification
VDI-NOo 2107, April I960

                          TABLE OF CONTENTS


      VDI Committee for Air Purification  .,....,...•.   iii

      INTRODUCTION r Permissible Immission Concentrations  ...     1

      General Remarks ......«.».	     2

1.    Occurrence of Hydrogen Sulphide .............     3

1*1   Occurrence in Nature  ...»o.	     3

1.2   Occurrence in Technical Installations   .........     3

2.    Properties of Hydrogen Sulphide 	 .....     k

3.    Effect of Hydrogen Sulphide   ..............     £

3.1   Effect on Man   	     5

3.2   Effect on Animals	. .     7

3.3   Effect on Plants	 .  . .     7

h.    Exposure Limits	~ . .,  . .     8

5.    REFERENCES	     9
                                - 11 -


     The VDI Committee for Air Purification is composed of experts in all
fields of importance for air purification.  These experts collaborate
with the Committee on their own responsibility and without compensation
and are proposed for the Committee by the following societies and institu-
tions :

     German Society for Hygiene and Microbiology
     German Society for Oil and Coal Chemistry
     German Society of Gas and Water Experts
     German Meteorological Services
     Society of German Chemists
     Society of German Iron Mine and Steel Mill Experts
     Association of Anthracite Mines
     Technical Inspection Associations
     Society of German Steel Mill Experts
     Society of Geraan Foundry Experts
     VDI Trade Section on Dust Technology
     Association of Steam Boiler Owners

     Scientists from Universities and Institutes in Biology,  Chemistry
        Forestry and  Agriculture  Human and Veterinary Medicine,  Metal-
        lurgy, Physics, and Technology
     Research Institute of the Cement Industry
     Federation of German Industry (Chemical Industry,  Oil Industry,
        Automobile Industry, etc.)
     German Federal Railroads
     Federation of German Farmers
     Federation of Community Associations
     Settlement Federation of the Ruhr-Coal District
     Competent Federal and State Ministries
     Institute for Water, Soil, and Air Hygiene of the Federal Public
        Health Service
     Public Inspection Services
                                 - ill -

                  Permissible Iiranission Concentrations

     The VDI Specifications on Air Purification are divided into the
following groups;

     1.  Permissible Iiranission Concentrations  (PIC-values)
     2.  Calc-ulatian of the Distribution of Dust and Gas
     3.  Restriction of the Emission of Dust and Gas
     It.  Dust and Gas Measuring Techniques,,

     In the evaluation of problems cf air pollution, the inner relation
of these four groups of specifications nsst. be considered,

     The VDI Specifications for Peradssibl© Iiranission Concentrations
concern the determination of limit values for  given types of air pollu-
tion.  The PIC-values of air-polluting substances are defined as those
concentrations in layers of the open air close to the ground and/or,
for dust, also ae those quantities of deposition on the ground which
may be considered in general as harmless., according to present experience,
for man, animal or plant when exposed for a given duration and frequency.

     The concentrations of air-pollv&ing substances in the open air vary
greatly.  For reasons of measuring methodology, the limit concentrations
are determined as mean values for giTs»~ periods of time.  As a rule, one
limit value each is determined for coati^acms  or intermittent exposure to
gaseous substanceso

     The limit value for continuous exposure (PIC^) is the maximum mean
concentration in & given meas»jred interral (©ogo5 half/hour mean value)
raider continuous exposure,

     During shorter periods, the limit vaX?;©,,  for msny substances, in
continuous exposure can be exceeded without danger*,  Duration, extent
and frequency of possible excess exposure cannot be uniformly stated
because of the varying character of the effect of such substances as well
as for reasons of measuring methodology.

     Concentration is indicated in mg/m^ of air and/or cra^/sP of air
(ppm • parts per million),,

     In the determination of PIC-values for dust deposition, different
ass-umptions are applicable on the basis of present experience,,  Measuring
intervals must extend in principle over longer periods.  The limit value
for dust deposition is indicated in g/m /time,

     PIC-values are valid only within certain ranges because of individual
differences of constitution and surroundings„  In themselves, they are
not a scale for the evaluation of suspected damage from emission,,  If
PIC-values are referred to in such cases, then this must be done in con-
sideration of all accompanying circumstances and only by experts familiar
with the pertinent factors.

     In the determination of PIC-values, the experiences and findings
are decisive which were gained for cases where only one type of air»
polluting substance is involved„  It is known that the simultaneous
existence of several such polluting substances changes the combined
effect but we are able only in special cases to develop specifications
for combined factors of pollution because of the great number of possible
combinations „

     As a rule, the PIC-values are valid only for the open air outside of
an emitter.  For purposes of comparison, the PIC-values are always contrasted
 'Vi*h    ,. the permissible work-station concentration (PWC-value) of
the respective gas, aerosol or dust, i.e. the present limit value for the
mean concentration of the substance in the respiratory air at the work-
station per 8-hour shift (German Research Federation, Committee on Testing
of Industrial Materials Injurious-to-Health, First Communication, December
1958.  Cf„ Federal Ministry for Labor and Social Matters, "Work Protection"
No, 12, 1958).

                            General Remarks

     Hydrogen sulphide is a gas with an objectionable odor and poisonous
over a large range of concentrations,  A reliable indicator of its presence
by a characteristic odor does not exist for man because perception may
be reduced at low and gradually rising or suddenly produced high concentra-
tions o  It has been relatively difficult in the past to establish the
degree of toxicity to man, animal or plant under continuous exposure to
very small amounts0  Man reacts especially sensitively to hydrogen sulphide.
Because of its highly disagreeable smell, the threshhold limit of normally
sensitive persons has been selected as PIC-value.  Reliable and representa-
tive evaluation on continued exposure to hydrogen sulphide for longer
periods within this range of concentration is not yet available to a
                                 - 2

 sufficient degree because there are still certain difficulties  in measuring
 and recording very snail amounts for hydrogen sulphide.   For these reasons,
 the PIC-value for HjS  can presently be established only  approxlnately.

                   1.   Occurrence of Hydrogen Sulphide

 1.1  Occurrence  in Natures

      Hydrogen sulphide is produced in nature primarily by the decomposi-
 tion of sulphur-containing amino-acids of vegetable and  animal  proteins
 by putrefactive  bacteria»  It develops principally in stagnant  and In-
 sufficiently aerated water,,  insufficiently maintained clarification in-
 stallations and  in latrine or manure pits.   It occasionally occurs in
 large amounts together with petroleum and/or natural gas (Alberta, Canada*;
 Lacq, Prance| Poze Rida ,  Mexico)  and also with sulphur deposits  (USA;
Mexico^  Vistula-San Bend, Poland),K To a lesser degree,  it also occurs
 in some thermal  sources  (Aachen,  Tolz,  etc.) and  in volcanic gases.

 1.2  Occurrence  in Technical Installationsg

     Hydrogen sulphide ©ontainlng waste gases may oc@ur  singly  or together
with  other similsr sulphtsr compounds primarily in the following industry
 •branches and enterprises 8

Mining  and Coal  Processings

      Gomb-astion  processes in mine  dtanps,
     Coking plants, gas  works, isarbaniziasg  plaats,
     Tar distillation  installationsj

ChemLaal and Related Industries8

     Cellulose and viscose factories (rayon,,  cellulose wool and film),,
     Rubber industry,
     Sulphur production  installations  (Glaus funuuses, Frasch process),
     Manufacturing installations for sulphur-eontmining  chemicals
        (carbor. disulphide, sulphur colors, ultramarine,  sulphur)j
     Phosphorus  couapounds^ pigments &a well  as lithopoue and zinc,
         barium,  and sodium sulphide),

Mineral  Oil Industryg

     Hydrogenation plants,
     Oil extraction installations,  refineries and cracking plants;
     Natwal gas production,  purification and processing installations?

 , ,n  .r.j j.^t ^i Smelters and Foundries g

     Blast furnace installations ,
     Slag -quenching installations $

         g lr; ai&stries and Trades for Vegetable Products 8
     Packing plants for fruit,, vegetables and jam,
     Sugar factories s
     Flix roasting plants 3

FrocesaJBg Industries and Trades for Animal Products 8
     Che«!i8 <»nd d^iry plants,          ,
     Wool scrubbing plants,
     Animal salvage plants (bone Bills, gelatin factories, etc.);

Mjcr.gllar.oous Industries g

     Chemical laboratories,
     Well installations,
     Drinking water and water supply treatment installations,
     Sewer installations,
     Sewage treatment installations (biological filters, settlement
        tanks, irrigation fields),

                  2o  Properties of Hydrogen Sulphide

     Hydrogen sulphide is a colorless, combustible gas and may form
explosive mixtures with airs  It is heavier than air and soluble in water,
in small aniaonss^ with a slightly acid reaction <,  In low concentrations,
hydrogen sulphide has the typical smell of rotten eggs which may no
       be perceptible, howa'rer, in higher concentrations.

     Physical and f shegiffial paropartiuss

            Formula                               HJ3
            Molecular weight                      3u*08
            Density (0°C, ?60 Torr)               1.5U kg/m3
            Boiling point (760 Torr)              -60^0
            Solubility in waters
                0°C, 760 Torr                     7.2 g/litHO
                20°C, 760 Torr                    6.0 g/lit

     Qualitative Demonstrations

     Smell similar to rotten eggs; moist paper saturated with lead acetate
solution assumes a dark-gray reflecting coating of lead sulphide (PbS)
by hydrogen sulphide .

     Quantitative Determinations

     Cf. VDI Specifications 2113 on Measuring Techniques (in preparation),

            3.  Effect of Hydrogen Sulphide (Cf „ References)

3ol  Effect on Mans

     Hydrogen sulphide in gaseous form enters the human body primarily
by way of the respiratory tract, acts as a cell and/or enzyme toxin and
can produce irreversible damage in the nerve tissue.  The gas irritates
the mucosae and the conjunctiva.  In high concentrations, hydrogen sulphide
is very dangerous and frequently produces death abruptly by paralysis
of the respiratory center.

     Hydrogen sulphide possesses no reliable indicator of its presence.

     The syndrome of hydrogen sulphide intoxication (sickness from H^
in industrial enterprises is subject to the Fifth Occupational-Disease
Regulation of 26 July 1952) leads to various diagnoses, particularly in
lighter stages and subacute manifestations.  We find a metallic taste,
fatigue, easy irritability, malaise, vomiting, diarrhea, insomnia,
vertigo.  In addition, under repeated exposure, skin affections may also
occur together with the disturbances listed below.

     For the diagnosis of hydrogen sulphide action, the following symptoms
are more reliables  conjunctivitis with reddening and lachrymal secretion,
irritation of the respiratory tract, pulmonary edema, damaged heart muscle,
psychic changes,   derangement of equilibrium (damage to the extrapyramidal
system), nerve paralysis, spasms, unconsciousness, circulatory collapse.

     Tolerance of hydrogen sulphide in the toxicological meaning does
not exist.  The olfactory sense is one of the most sensitive indicators
of hydrogen sulphide.  Injury to health through hydrogen-sulphide con-
centrations below the olfactory threshold is not definitely known.  It
is probable that a slight excess above the limit of 0.1 cm-Ym £^ 0.15
      (0.1 cmVnP (ppm) • 0.16 mg/m3) is without risk.
     Under long continued exposure to concentrations at the limit of
perceptibility, definite injury or interference have yet not been observed,
An evaluation only by small ip not reliable because of individual differences

                                 .5 -

of sensitivity.  Moreover, hydrogen sulphide concentrations increasing
above the olfactory threshold are not perceived proportionately stronger.
Because of the increasing olfactory sensitivity, the smell is even less   .
objectionable above 200 cm^/m^ .~ 320 mg/m^.  At over 700 cnP/nP ^
c=ill20 rag/m^, death may oseup rapidly and practically without any
olfactory sensation.  Since olfactory sensation becomes easily neutralized,
this is especially important for subjects under continued exposure to
hydrogen sulphide.  On the other hand, human subjects may become more
sensitive to the smell after frequent intermittent exposure to hydrogen

     Through simultaneous pollution of the air with carbon disulphide,
mercaptan  and similar substances, the smell may be reinforced and give
the impression of a higher concentration of hydrogen sulphide.

Effects on Man from Indications in Literature
700 plus
1120 plus
Relatively quickly fatal, possibly without previous
olfactory sensation
Dangerous concentration under 30~minute
or less
No serious damage after one hour but intense local
Slight syaptaffis after several hours
Strongly perceptible but not intolerable
Small definitely perceptible
Smell slightly perceptible
Olfactory threshold


     Hydrogen sulphide may produce synergistic intoxications in mixtures,
e.g., with carbon disulphide, hydrocarbons, carbon monoxide and small
amounts of irritant gases .•  When it occurs in combination with carbon
disulphide, for example, the PWC-value for hydrogen sulphide is reduced
to one-half in many countries»

3.2  Effect  on Animal ^.(References  2, 10, lli,  15, 31) s

     In domestic animals, hydrogen sulphide produces the same manifesta-
tions of  sickness as  in man and at approximately the same concentrations
of the gas.

     Spontaneous injuries were observed, for  example, in stables with
built-in  manure pits  (lU).  The content of gas in the air of the stable
in this case amounted to about 100-300 cm3/m3 (160-U80 mg^/m^) of hydrogen
sulphide  and there were present at the same time about 2000-3000 cmVm^
of carbon dioxide and 100-200 em3/m3 of ammonia.

     PIC-values;  Same as for man.

3.3  Effect  on Plants (References  Ij, 5, 12, 19, 20, 21, 23,
                        21, 25, 29);

     It is generally  believed that plants are less sensitive to hydrogen
sulphide  than man.  In the investigation of the effects of sulphur dioxide,
however,  it'has been  determined that chronic  injury through the accumula-
tion of sulphur compounds is possible«,  This must also be assumed for
hydrogen  sulphide, disregarding the blocking  of the respiratory enzymes
due to the bonding of the catalytically acting iron components.  The
chloroplasts are attacked first0

     When dissolved in water or in the moisture of the soil, hydrogen
sulphide  may have a damaging effect by way of the plant roots.  Such
damage may be produced by a content of 1.5-3 cm^/m^ *zz 2<>U-U.8 mg/rn^
in the water absorbed.  Plant components above ground are in general
less endangered by hydrogen sulphide.  Sprouting plants are effected more
strongly  than older plants and this is also true for younger leaves more
than for  older leaves0  H®u®vers germination is only interfered with by
an excess beyond a certain ©eneentration whereas hydrogen sulphide in a
low ooncentration may even b© activating for germination.

     Sensitive ares

     tobacco, radish, poppy p soy beans, clover, salvia, cosmea. gladioli
     and, under exposure for a prolonged period to 30-50 cm^/nH f^> W3-80
     tomatoes, radish, cucumber, buckwheat, asters, salvia.

     Less sensitive ares

     sunflowers,, peppers ricinus, cornflowers, nasturtium.

     The resistance of young cereal plants to 80 cm /m3 ^ 128
becomes greater in the following order:

     barley, rye, oats, wheat.

     Least sensitive ares

     peach, apple, cherry, strawberry, carnations, coleus, portulaca.

     Plants are able to prosper without damage in air with hydrogen-
sulphide concentrations close to the olfactory threshold.

     Typically exterior symptoms of damage by hydrogen sulphide in plants
are manifestations of wilting without typical discoloration which starts
from the tip of the leaf.

     The toxic limit for plants may be assumed, according to present
experience, as 1.5 cm3/m3 ^2.5 mg/m3 of hydrogen sulphide in air.
                          ho  Exposure Limits

     The PIC-values are based on the guide values of the effect on man.
According to present experience, continued exposure does not produce
injury as long as the half-hour mean value does not exceed 0.1 cm3/m3'£='
^0.15 mg/m3.
PICC - continuous exposure

PICj • intermittent exposure
  value (permissible excess
  above PIC(j)
FWC-value (35) (permissible
  work-station concentration)
  as comparison
0.1 cm3/m3 
                            5.  REFERENCES

          (Only important individual and standard publications
                              are listed).

 1.  Baader, E. W. i  Occupational diseases, Urban and Schwarzeriberg,
       Munchen-Berlin 195a.

 2.  Blaser, E. :  A contribution to the knowledge of hydrogen-sulphide
       intoxication in animals by manure gases, doctor thesis, Bern

 3.  Bodurtha, Jr., F, T. !  Flare Stacks - how tall?  Chem. Eng.  65
       (1958), 25, p. 177/80.

 lu  Czurda, V.,:  Hydrogen sulphide as ecological factor of algae.
       Zbl. Bakter., Parasitenk., Jnfekt., Abt. II 103 (19M) p.  285/311.

 5»  Davenport, S. J. and G. G, Morcis:  Air Pollution, A Bibliography,
       Bull. 537, U. S. Bureau of Mines, 1951i.

 6.  Duan-Fen Djuy:  Findings on the determination of maximum per-
       missible hydrogen-sulphide concentrations in the atmosphere,
       Hyg. and San0, Moscow 1959, No. 10.

 7.  ElkLns, H. B.:  The Chemistry of Industrial Toxicology, John
       Wiley and Sons, New York 1959.

 8.  Flury-Zanggers  Manual of toxicology, J. Springer, Berlin 1928.

 9.  Flury-Zernik!  Types of injurious gases, vapors, fog, smoke  and
       dust, J. Springer, Berlin 1931.

10.  Frohner, E. and R0 Volker:  Manual of Toxicology for Veterinaries,
       F. Enke, Stuttgart 1950.

11.  Fuhner-Hecht-Wirths  Medical Toxicology, G. Thittne, Stuttgart 1951.

12.  Haselhoff, E., G. Brederaaan and W. Haselhoff :  Creation, identifica
       tion and evaluation of smoke damage, Berlin 1932.

13.  Henderson-Haggards  Noxious Gases, Reinhold Publishing corporation,
       New York
  i.  Hofmann, P . s  Hygienic Investigation of Air in Dairy Stables with
       Special Reference to Built-in Manure Pits, Z, Infekt. krkh.,
       parasit. Krkh8 and Hygiene of Haustiere (1928), p. 238/62.
                                 . 9 .

15-  Klimmer, M. :  Veterinary Hygiene and Health Care of Domestic
       Animals in Agriculture, P. Parey, Berlin 1921*.

16,  Loginowa, R. A. :  Bases for the Determination of Maximum Possible
       Concentrations of Hydrogen Sulphide in the Atmosphere.  Ins   W, A.
       Rjasanow, Maximum Permissible Concentrations of Atmospheric
       Pollution, Medgis, Moscow 1957, Vol. 3, p. 63/83.

17.  McCabe, L. C.r  Air Pollution, McGraw Hill Book Camp., Inc.,
       New York-Tor onto-London 1952.

18.  McCabe, L. C. and G. D. Clayton;  Air Pollution by Hydrogen
       Sulfide in Poza Rica, Mexico, Arch. Ind. Hyg. Occup. Med. 6
       (1952), p. 199/213.

19.  McCallan, S. E., A.Hartzell and F. Wilcoxon:  Hydrogen-Sulfide
       Injury to Plants, Contrib. Boyce^-Thompson Inst. 8 (1936), p.

20.  Magill, P. L., F. R. Holden and Ch. Ackleys  Air Pollution Handbook,
       McGraw Hill Book Comp., Inc., New Tork-Toronto-London 1956,  Sect.
       9, p. 25.

21.  Marx, Th.:  Contribution to the Knowledge of Vegetable Toxins  in
       Municipal Garbage, Dung.,  Bodenk.  51 (1950), p. 229/3it.

22.  Moeschlin, S.s  Clinic and Therapy of Intoxications, Third Edition,
       G. Thieme, Stuttgart 1959.

23.  Nakamura, H.:  On the assimilation of Carbonic Acid by the Lower
       Algae in the Presence of Hydrogen Sulphide, Acta phytochim.
       10 (1938), p. 271/81,

2ko  Negelein, E»s  Unpublished experiments quoted by 0. Warburg, Ber.
       Dtsch. Chem. Geso, Abt. Vol 58 (1925) p. 1001/11.

25-  Okajima, H., S. Takagi, N. Takshashi and T. Honda:  Physiological
       Behavior of Hydrogen Sulphide in the Rice Plant, Ninth Communication:
       Interference -with Growth and Development in Plants Treated with
       Hydrogen Sulphide, Bull. Inst0 agric. Res., Tohoku  Univ. 9  (1958),
       p. 193/225, ref. Landw, Zbl. (1959), 2, p. 3liO.

26.  Patty, F. A.s  Industrial Hygiene and Toxicology, Vol. II, Inter-
       science Publishers, New York-London
27.  Schuler; B.s  Clinics of Intoxication by Hydrogen Sulphide, Verh.
       Deutsch. Ses. f. Arbeitsschutz, Bol. 2, p. 28/38, Dr. D.  Steinkopff,
       Darmstadt 195U.
                                   10 -

28.  Schur, R. L. :  Comparison of the Toxic Effect of Natural Gas in the
       Presence of Hydrogen Sulphide and Pure Hydrogen Sulphide, Phar-
       makolog. and Toxikol. (UdSSR) 12 (19l*9), No. 1.

29.  Sorauer:  Agricultural Yearbook 33 (I90li), p. 585/661*.

30.  Strum, I. J.:  Experimental Data on the Combined Effect of CO and
          , Physiolog. Journal (UdSSR) 2k (1938), 3, p. 62V28.
31.  Supfle, E.:  Hygiene in Stable Construction, Dtsch. Tierarztl.
       Wschr. 38 (1930), p. 225/30.

32.  Taeger, H.s  Occupational Diseases, J. Springer, Berlin 191*1.

33*  Thomas, I vie, Abersold and Hendricks, Ind. Eng. Chem. 15 (19li3),
       p. 28?.

31;.  Findings and Experiences in Occupational Medicine from Reports
       by State Occupational-Medicine Physicians of the German Federal
       Republic (1952/5W, Ko{tlen-Yerl., Bonn 1957.

35*  German Research Federation, Committee on Testing Industrial Mate-
       rials InJurious-to-Health, Coranunication 1, Dec 58, cf . Federal
       Ministry for Labor, "Worker Protection", No. 12, 1958.
                                 - END -
                                   n -

2090    Sources of Air-Polluting Substances
2091    Restricting Dust Emission From Forced-Draft Boiler Installations,
           Capacity 10 Ton/Hr and. Over, Hard-Coal Fired with Mechanical
2092    Restricting Dust Emission From Forced-Draft Boiler Installations,
           Capacity 30 Ton/Hr and Over, Hard Coal-Dust Fired with Dry Ash
2093    Restricting Dust Emission From Forced-Draft Boiler Installations,
           Capacity 30-600 Ton/Hr and Over, Hard Coal-Dust Fired with liq-
           uid Ash Removal
2094    Dust Prevention - Cement Industry
2095    Dust Emission From Induced-Draft Ore-Sintering Installations
2098    Restricting Dust Emission From Natural-Draft Steam Generators,
           Capacity 25 Ton/Hr and Less, Lignite-Fired with Stationary  or
           Mechanical Grates
2099    Restricting Dust Emission in Blast-Furnace Operation
2101    Restricting Dust Emission From Copper-Ore Smelters
2102    Restricting Emission of Dust From Copper-Scrap Smelters
2103    The Restriction of Chlorine Gas Emission
2104    Terminology in Air Purification
2106    Permissible Immission Concentrations of Chlorine Gas
2107    Permissible Immission Concentrations of Hydrogen Sulphide
2108    Permissible Immission Concentrations of Sulfur Dioxide
2109    Restricting Emission of Hydrogen Sulphide and Other Sulphur-Con-
           taining Compounds, Except Sulphur Dioxide, From Gas Generators
           in Coke,  Gas, and Coal-Constituent Processing Plants
2110    Restricting Emission of Sulphur Dioxide From Coke Ovens and  Gas
2115    Restricting Emission of Dust From Manually Operated Central-
           Heating Boilers, Capacity 600, 000 KCAL/Hr and Less, Fired with
           Solid Fuels
2281    Restricting the Emission of Fumes From Diesel-Engine Vapors
2284    Restricting Emission of Dust and Sulphur Dioxide in Zinc Smelters
2285    Restricting Dust and Sulphur-Dioxide Emission From Lead Smelters
2290    Restricting Emission From Gas Generators in Coke and Gas Plants
2292    Restriction of Dust Emission in Anthracite-Briquet Factories
2293    Restricting Emission of Dust in Anthracite Processing Installations
2302    Restricting Emission of Dust, Tar Mist and Gas when Charging Coke
2105    Permissible Concentrations  of Nitrous Gases