Document LgDmjeGDyGbeLM7680Lnz1jbz

* *j < * * :h * ,, ,,,\ j ;t _ > ' - ' * ' *T .. 4 V -1 .1*' . f-?4. , i-M* \*4 . \2-. *,-- . <t y *. * *. it *T t. *** *4. * ritti **.. i tVM 1, u. . *1i Min <( ^ t< U-# +1 * * . I .# ** Ni|t < < vi v ^ f* Ill* *v*v * >#* * - * * * i *. ;<* mi e *>*% 4 **f t/V(. * ^fivk4 *% Ijr ' <* * i 1* t\* ! ****** fcl f*4 ss J.1 C -*K tsf !"*' 4***1 t* ``v* * * * .*t# -'K ti ' f* >** i* v r.j i *%,, #14' *"4 r * I* f >X r- s * *** K ^ ** *4 t'' t ' .; t * . ' `h V - *J 4 %\* 1' .* *- 4 ` * '* * * *,/*** 4 * iJ- / --** 4 'Jai ` j * *. > x a. * - !; v S<i V 4* 1 IO in CO O t ' i>- ` . . -t ,r \ '- `J to* wl> Wf to minimize air pollution from clicm. or power plants. the atm. by odor, by its effect on the sensitivity of the eye, and ` J.C.Tallman by electroencephalography are 0.084, 0.080, and 0.003 mg./tn.1, . upr RopW continuous determination of nitric oxide con resp. Rats exposed for 93 days to 0.4 mg./cu. in. showed slight dition in exhaust Rases. T. Singh, K. F, Sawyer, E. S. changes in motor chronaxy, HS-eoncns., and cholinesterase ac .,,i, and L. S. Coretto (l/niv. of California, Berkeley). tivity which were accentuated by starving. An atm. coutg. 0.04 'i'Jlut. Coulr. Ass. 18(2), 102-5tl9GS)(Eng). The rapid mg./m.* did not produce any observed effects. The recom j SO levels in exhaust gases is required both for lab, studies mended max. permissible concn. is 0.05 mg./m.* ishattst emission characteristics of combustion engines and John Howe Scott . aline inspection of motor vehicle exhaust. A continuous 62476x A toxicological study of Bulgarian reactive dyes. I. "nth continuous anal, method for measuring NO was dem- V. Khrisieva (Katcdra higiena, Plovdiv, Bulg.). Khig. Zdraven- uetl. Rapid oxidn. of NO to X02 is obtained through par.anc 10(4), 3&9-94(1967KBulg). The toxicity of new Bulgar Mtion. NOa conens, are detd. by means of an uv absorp- ian dyes used in the textile industry Hisulone orange (I) and Hisa- .'Ivliiiiqiie. NO conens, between 100 and 5000 ppm. were lone brilliant red (II) was tested in white mice and rats. Aq. ,.jrcd and response time of about 20 sec. obtained. The sotns. of I and II at conens. 5, 10, and 2t)l7 were administered .-see oi unburned hydrocarbons in the exhaust sample has an intraperitoneally or orally. The LDij of I was found to be 435 effect on the results of this technique which requires in mice and 700 in rats; that of II was in rats 840 mg. 'kg. intra r the removal of hydrocarbons or adjustment of 03 concn, peritoneally. The LDic of I and II after oral administration were RCXV 14 and 15 g./kg., resp. Manifested dystrophic changes were ob t;70r The control of fumes from a hot blast cupola by high- served after higher doses of I or II. Petr Skrabatiek ,!jy scrubbing without appreciable thermal buoyancy loss. 62477y Urinary excretion of nickel in subjects exposed during Sullivan and R. P. Murphy, Ini. Clean Air. Congr., electrolytical production of nickel, I. Klucik and R. Kcmka (Vys- Loudon 1966(Pt. 1), 144-6(Eng). The control of fumes kumny Ustav Hyg. Prace, Bratislava, Czech.), tiratislav. cuue of the more recently developed metallurgical processes Lek. Listy 48(9), 523-9G9G7)(Slo). The urinary excretion in 6 -ints difficult problems. Choice of equipment is limited vir- persons decreased exponentially with time to 0.100 zfc 0.048 on _,v to electrostatic pptn., fabric filtration, or high-energy the 6th day and to 0.066 0.020 7 Xi./ml. on the 7th day after "".ibing. The last is the least costly. From the air pollution terminated exposute to an atm. contg. 0.7-1.26 7 Xi/l. in the if.tsieani production and loss of thermal buoyancy of the dis form of NiCOi and NiSOi aerosols. With regard to the av. Xi ced gases are important disadvantages. A recentdustaUa- content in the urine of normal unexposed persons (0.098 d: 0.042 Has designed in which the heat is e.xtd, from the flue gas be- 7/ml.), the excretion process thus seems to require 6-7 days. ... scrubbing and re-introduced afterwards. As a result, a L. J.Urbanek ,<:<rand drier plume which has no tendency to down-wash was 62478z The hygienic characteristics of trace element fertili cvcd. George A. Robinson Sr. zers (PMU-7) production dust. T. D. Lienko (I Mosk. Med. :471s The biological effect of caprolactam and its sanitary Inst. im. Sechenova, Moscow). Gig. Sanit. 33(11, 51-4(1908) tunic assessment as an air pollutant. I. M. Krichevskaya fRuss). PMU-7 is a finely powd. dust contg. SiO* 30-5, Zn .Tittovsk. Med. Inst., Kamcrovob Gig. Sanit. 33(1), 22-8 15-20, AUOj 6-7, Fe;Oi 10-13, CaO 0-3, MgO 0.5-1.0, Mn 0.5, '.\(Russ). The thresholds for detection of caprolactam in and Mo 0.02Without special care, there is danger from the t am. by odor, by electroencephalography, and by its effect dust during manuf. After intraperitoneal introduction, the j"( sensitivity of the eye are 0.3, 0.2, and 0.18 mg./m.*, resp. LDa> for mice is S33.5 mg./kg. Rats were exposed 4 hrs, daily, exposed to 0.00 mg./m*. for 82 days showed changes in 6 days a week for 4 months, to an atm. contg. 5 mg./m.* Re oilar chronaxy, cholinesterase activity, and coproporphyrin duced growth and erythrocyte counts and morphological changes ition. A concn. of 0.024 mg./m.1 did not produce any ob- in the lungs were observed. John Howe Scott i-td physiol, changes. The recommended max. permissible 62479a Poisoning, with hydrogen sulfide in production of jS. both for a single and continued exposure is 0.00 nig./tn.* pinene mercaptan. Miroslav Bejsovec, Josef Budiovsky, and John Howe Scott Borivoj Lehky (KUXZ Scveroceskeho Kraje, Usti, Czech.). -'4721 Asthma and isocyanates. J. M. Mantz, B. Ham- Prac. Lek. 19(9), 413-10(19G7)(Czech). A case is described -a, J. D. Tcmpc, and A. Meyer (Serv. Reanimation Clin. with a toxic impairment of the brain cells and capillaries and t. A C.H.U. Hop., Strasbourg, France). Arch. Mai. Pro}., secondary edema of brain. It was followed by a slight non- -c. Secur. Soc. 28(9), G73-G(19t57)lFr). Some 05 cases of a uniform decrease in the intellectual capacity prevailing over 2 **cuhr type of asthma were noted in a Spanish plant dealing years, marked drop of spontaneous activity, marked disorder of - Desmodur T, an isocyanate mixt. used in nianuf. of syn- the retention of fresh memory and of associative learning. ex rubbers, plastics, paints, etc. The effective constituents L. J. Urbanek ' toluene 2,6-diisocyanate, and the 2,4-isomer. This is a 62480u Thermal decomposition products of polyfvinyl chlo {them., since it has many free isocyanate groups, and is vola- ride). Toshio Tsuchiya and Kikuo Sumi (Div. Bidg. Res., * toom temp, and, therefore, inhaled easily. Tests show Natl. Res. Council, Ottawa, Can.), J. Appl. Chem, (London) *; the particular symptoms are due to Desmodur T. Both 17(12), 364-6(1907)(Eng), The toxic thermal decornpn. prod ation and allergy arc discussed as causes, and the aromatic ucts of poly(vinvl chloride) are detd, by pyrolysis followed by ''o is thought to be more responsible than the isocyanate group gas chromatographic anal, and their toxicities assessed by cam- -* Desmodur II (hexamcthylcnc diisocyanate) causes no symp- paring the ratio of the concn. of a volatile product evolved when 1 ;i- Since there is no treatment, only preventive measures are g. of the original material is dccompd. and the decornpn. products vtsted, including immediate removal of affected workers arc diffused in a vol. of 1 m.*, to its lethal 130 min.) concn. HC! is 1 die area where these isocyanates are bandied; compulsory the main deeompn. product followed by benzene which is always ' * goggles, protective gloves and filters; control of the amount found in the product in both an inert atm. and air. CO and ** chemical present. In previous work by Henschler, 0.02 COj are formed only in air and H>, methane, ethane, e.hylene, '' 1900 is considered satisfactory. The authors consider and PhMe are obtained in both He and air. The similarJ y of the 6.005 parts/1000 is better. M. I. Rawnsley volatile decornpn. products found in the 2 different atms. sug *4'4u Hygienic features of the production process for gests that the decornpn. mechanism is nonoxidativc and essen of less-common metals. I. Y. Shalganova (I. Mosk. tially thermal. HCl was the highest toxicity, being 3-10 times ""Inst. im. Sechenova, Moscow;. Gig. Sanil. 32(12), 28-31 as great as that due to CO when polyfvinyl chloride) is dccompd. /"Russ). The following LDM in mg./kg. are reported for in the presence of air. CKIN " niobate, Ta;Cb, and XbjOj all greater than 4000; ZrCU, 62481v Substantiation of the principles and methods for `v-Midi, 830.0; NaF, 97.0; K,ZrFt, 97.5; K-TaF;, 110.0; toxicological evaluation of volatile substances escaping from :0, 130.0. Exposure of guinea pigs for 4 months to atm. synthetic polymer products. I. M. Trakhtenberg, V. D. Bar * mE-/m * KjZrFc or KiTaFi produced redns. in Ac- tenev, I. V. Savitskii, and V. E. Balashov (Kievsk. Mca. Inst., phosphatase, and albumin conens. in the blood. Kiev). Gig; Sanit. 33(1), 97-9(1908)(Russ). The planning, ... John Howe Scott design, and execution of expts. leading to toxicologic evaluation The toxicity of aerosols of sodium carbonate and sul- of industrial air contaminants such as formaldehyde, phenol, tolutions. A. L. Rcshetyuk and L. S. Shevchenko (Do- styrene, epichlorohydrin, amines, acrylates, cumene hydro "?"ch.-Issled Inst., Donetsk. Gig. Tr. Frofzabol). Gig. peroxide, phthalic anhydride, sulfides, cyanides, fluorides, org. lll-13(19G8)(Russ). Rats exposed to an atm. chlorides, and organophosphorus compds. are discussed. '-is tng./m.* of dust obtained by spraying a NajCOi CPJR 'V'tg sulfonol showed greater local morphologic changes 62482w No abstr. ;ungs and redns. in tissue ascorbic avid conens. (hm did 6?4P3x Ultraviolet photolysis of sodium nitrate solutions in j;< vd u> atm. .on',,;. 71.' -- J.J ms`. in. w:uiuiit t.iu .->ul- the laboiatory and by sunlight. E. G. Gori, G. L. Pttricmii, and . Hie reconiinondtd nux. for atm. du-ts omtg. Na.COi H. M. Rupee vCuuro Nucl. Aerosol!, Rome), Xniurc 217(51251, ind 5 mg./m.1 depending on whither an anionic surface 248-9(l!>;.S;(Eng;. The photolysis of aq. NuNCb by oriiueiai ** prC-'-iH or not. John liowe Scott uv radiation and sunlight was studied. Artificially irradiated The hygienic significance of small concentrations of samples were analyzed for NO- - using the Gricss reagent and, by ./.wtinein the atmosphere. X. R. Kosiborod (Novosibirsk. titrating with MnOi-, the amts, of near uv light absorbed were "',`"5Rd. Sanit. Inst., Novosibirsk). Gig. .Sanil. 33(1), detd. The formation of NOj- was enhanced by the presence of `` '9C8)(Russ). The thresholds for detection of EtiNlI in Cl - owing to the stabilization of the X oxides evolved by XOC1 CJ_ 364 Tsuchiya & Sumi: Thermal Decomposition Products of Polyvinyl Chloride / c THERMAL DECOMPOSITION PRODUCTS OF POLYVINYL CHLORIDE By YOSHIO TSUCHIYA and KIKUO SUMI When plastics are involved in a fire they may yield toxic decomposition products. Some quantitative data on the decomposition products of plastics arc available in the literature, but it is difficult to assess the danger from the different amounts of various products because of the absence of a suitable method of evaluation. The authors have proposed a method of evaluation based on pyrolysis followed by gas chromatographic analysis and have used it to assess toxicity from various thermal decomposition products of polyvinyl chloride. Hydrogen ciiloridc was found to be the main toxic decomposition product. Introduction The increasing use of plastics and other organic polymers raises the possibility that when involved in a fire they may yield toxic decomposition products in quantities sufficient to produce a dangerous atmosphere. Some quantitative results on the decomposition products of plastics arc available in the literature, but it is difficult to compare data because of differences in experimental methods and differences in presentation of experimental data. Jt is also difficult to assess the danger from the different amounts of various decomposition products because of the absence of a suitable method of evaluation, in view of the above factors, the authors believe that a need exists for a systematic study to provide quantitative results on the volatile decomposition products of a wide variety of plastics in both inert and oxidising atmospheres. A need also exists for a method of assessing danger from the different quantities of decomposition products. This investigation was carried out to meet these needs. Polyvinyl chloride (PVC) is the plastics material that has probably received the most attention from fire authorities because of its relatively wide use and the possibility of its thermal decomposition leading to the formation of toxic gaseous products. This polymer was, therefore, selected for the present study. Coleman & Thomas1 determined the combustion products of PVC and other chlorinated plastics using a static system. The specimens were decomposed jn a llask over a temperature range of 300 to 1000\ The ratio of plastics to air was varied by using different weights of sample, and the combustion products were analysed by conventional methods. Schriesheim* employed a similar method over a temperature range of 250 to 5503 and analysed the products of combustion by a mass spectrometer and chemical methods. Stromberg et aid studied the mechanism of thermal decomposition of PVC in vacuum. The volatile products were analysed by mass spectro metry and found to consist almost entirely of hydrogen chloride and small proportions of benzene, toluene and other hydrocarbons. Gilbert & Kipiing4 investigated the carbonisa tion of PVC and other vinyl polymers by decomposing the specimens, under vacuum, in an inert atmosphere and in air. After removal of hydrogen chloride the residue was de composed and the products were analysed by gas eh to mat ography. Jn the present investigation the thermal decomposition products of PVC were determined, firstly, in an inert atmos phere and, secondly, in air. A flow system was adopted OU 7356 instead of the static system used by other investigators,1'3 because the decomposition conditions during an experiment can be more closely defined in a flow system than in a static system. Material Experimental, The PVC used in this study was a commercially available, general purpose resin in powder form. It did not contain any plasticiser. Thermal decomposition PVC was decomposed in a furnace through which inert gas or air was passed and the gaseous products were collected in a flask. The sample was weighed in a ceramic boat, to which a stainless steel wire and a piece of iron were attached, so that it could be moved inside a 19-mm diameter tube to the hot zone of the furnace by means of an external magnet. The furnace temperature was maintained at isothermal values of 350, 600 or 850\ Helium was used to provide an inert atmosphere in one series of experiments and air was used to provide an oxidising atmosphere in the other scries. After some preliminary studies a gas flow rate of 450 cm3 per min was adopted. This corresponded to a mean linear velocity of about 160 cm per min. The sample weights selected for this study were 0-5 g in helium atmosphere and 0-5 and 0-25 g in air. The amount of air used during each experiment was slightly in excess of that required for complete com bustion of 0-5 g of PVC to carbon dioxide, water and hydro gen chloride. The smaller weight of 0-25g was also used in an effort to examine the influence of effectively increasing air supply on the formation of decomposition products. The higher boiling components of the decomposition products were collected in a U-tube filled with glass beads and maintained at 0. The unreacted gas and the remainder of the volatile decomposition products were collected in a 3litre flask that had been evacuated prior to the experiment. The sample was kept in the furnace until the gases filled the flask. Each experiment lasted about 8 min. Analysis Gas chromatography was the main method used in the analysis of decomposition products. As these were compowv of widely difi'ciing tnateri.'is. three chronuHOgrupme tuf.ditions had to be employed (two with a thermiitor-type thermal conductivity cell detector, with different columns). First a molecular sieve 5A (60- to SO-mcsh) column of length 2 m and diameter in. (0-6 cm) was used with the J. appl. Chcin,, 1967, Vol. 17, December ,11 -U.-W J-TS-+J., Tsuchiya & Sumi: Thermal Decomposition Products of Polyvinyl Chloride 365 I inductivity detector at room temperature and a 1M1( (helium) flow rate of COcnvVmin for the deter' ,non of hydrogen and carbon monoxide. Second, a , j.0l (60- to 80-mesh) column of the same length and cter as the molecular sieve column was used at SO1, for ''"determination of carbon dioxide and chlorine. For \r.tiu'*vc ann!>sis with the thermal conductivity detector ',J- response of the detector was calibrated against its res- to pure eases. ' hvdrogcn flame ionisation detector was used for the tJ condition, with another silica gel (60- to 80-mcsh) ; iliimn of length 6 ft (1-Sin) and diameter in. (0-3 cm) (,,r determination of various hydrocarbons. A programmed temperature of 80' for 5 min., followed by a heating rate of 10 min. up to 300', was used with a carrier gas (helium) :',nv rate of 30 cm3/min. Most of the peaks of the chrojnatoframs obtained under this condition were identified by comparison with retention times of pure materials. Identifica tion of some of the peaks was further confirmed by trapping ihc diluents, followed by analysis with a mass spectrometer. For quantitative analysis with the flame ionisation detector the response of the detector to n-butane was measured, and approximate substance specific correction factors' according lo Kaiser's definition,5 were used to calculate the response of other components. A calcium chloride trap was placed at the discharge end of the furnace tube to remove water vapour evoked. Some hydrogen chloride was absorbed by water vapour and was therefore trapped; the rest of the hydrogen chloride was determined along with carbon dioxide by a gravimetric method in which ascarite was used. The amount of hydrogen chloride not absorbed in water vapour was determined by subtracting the amount of carbon dioxide previously deter mined by gas chromatography. In an effort to deicrntinc chlorine, if present, a sensitive colorimetric detector tube (Kitagawa) was used. This de tector is recommended for concentrations of 1 to 40 ppm. Results and discussion The results of the determination of the volatile thermal decomposition products of PVC in an inert atmosphere and in air are given in Table 1. They are reported as percentage by weight of original polymer, and are based on means of two or more repeat tests. The main decomposition product of PVC was hydrogen chloride. Almost all the chlorine in PVC was converted to hydrogen chloride. The amount of hydrogen chloride pro duced in an inert atmosphere approached the theoretical value expected from PVC. The amount determined in an oxidising atmosphere was slightly lower, because water vapour pro duced in an atmosphere of air absorbed some of the hydrogen chloride. The amount of hydrogen chloride absorbed in water was intentionally neglected and the lower value re ported because the toxicity of hydrogen chloride produced at a fire is primarily due to the gas. The amount absorbed in the water would condense on cool surfaces and play a comparatively minor role. If this amount had been included, the results for hydrogen chloride would have approached the theoretical value because no appreciable amounts of other chlorine compounds were found in the decomposition products. Neither chlorine nor phosgene was detected. The minimum amount of chlorine that could have been determined in the present investigation was 0 003 wt.-% of the original polymer. The results for the two different sample weights were very similar. At the lower sample/air ratio, slightly more carbon dioxide was produced at the expense of hydrocarbons. The highest carbon monoxide concentration was found at 600'; the amount was less at 850' because of further oxidation to carbon dioxide. Benzene was always found in the product in both an inert atmosphere and air. The formation of benzene and other aromatics can be explained on the basis of the removal of hydrogen chloride from the polymer, producing a polyene system followed by the formation of stable six-membered rings.5 The similarity of the volatile decomposition products of PVC found in two different atmospheres suggests that the decomposition mechanism is non-oxidativc and essentially thermal. The only oxidation products found were carbon monoxide and carbon dioxide. Other oxidation products such as acids, aldehydes, alcohols, ketones, etc. were not found. This observation is in agreement with the author's experience with the decomposition of polyethylene in air. Efforts were made to assess the danger that might arise from various quantities of thermal decomposition products of PVC as determined in the present investigation. A literature search was undertaken to find data on relative toxicity of different materials. The most detail available is on maximum allowable concentrations of gases and vapours at which no adverse effect is expected.6^8 Some information is available on Hgher levels of concentrations such as those fatal to animals in a short time and the authors believe that such data would be more applicable to fire situations than the maxi mum allowable concentrations. Difficulties were experienced in finding consistent data on " Temp, of dccomp., c 'Vt of sample, g Atmosphere Decomposition products, wt.- % sample HC1 CO CO, H: CIC CjHf, C3IC Benzene Toluene Residue 350 0-5 He 53-2 ____ *_ -- ____ ____ 5-9 0 05 37-4 ITable Decomposition products of PVC 600 0-5 He 55-5 -- --- 0 06 10 0-69 0*52 5-6 0-67 6-3 850 0-5 He 57-9 --.-- 0-47 V2 6-32 2-5 5-9 0-87 51 350 05 Air 47-2 1-0 1-7 -- --* ,-- -- 5-4 -- 40-2 600 0-5 Air 46-0 35-6 40-8 016 1-7 014 0-63 4-7 0-22 2-4 850 0-5 Air 40-6 16*6 54-8 0-50 3*4 0 06 1*3 3*1 0*89 -- OLI 7357 350 0-25 Air 48*5 1*2 2*5 -- -- -- 5*1 -- 39*5 600 0-25 Air 42*3 43*0 65*7 on 1*7 0*14 0-3S 4*8 0*18 0*3 850 0-25 Air 24*3 18*5 99*7 0*37 2*4 0U3 0-41 1*3 0-31 -- J. appj. Client., 1967, Vol. 17, December ct 366 Tsuchiya < Sunii: Thermal Decomposition Products of Polyvinyl Chloride Temp, of dccomp., c Wl of sample, g Atmosphere Toxicity,t ~ ~ HC1 CO CO, car* Total toxicity 350 0-5 He 0-33 -- -- 0003 0-33 Taule H Toxicity from decomposition products of PVC 600 0-5 He 0-34 __ 0 003 0-34 850 0-5 He 0-36 ,__ __ 0003 0-36 350 0-5 Air 0-29 0-002 0-00004 0-003 0-29 COO 0-5 Air 0-29 0-07 0-001 0-002 0-36 850 0-5 Air 0-25 0-03 0-001 0-001 0-28 350 0-25 Air 0-30 0-002 0-00006 0-002 0-30 600 0-25 Air 0-26 0-09 0-002 0-002 0-35 8 0 A 0 0 0 0- 0- the relative toxicity' of the main decomposition products of PVC for very short exposures. Data on concentrations of gases and vapours considered fatal to man in a 30-min ex posure (cf) were assembled. Toxicity (/) dije to a gaseous or volatile product was assumed to be proportional to its con centration and to its relative toxicity (tr) i.e., txet,. Relative toxicity was defined as: /, = --. Cl The toxicity of a decomposition product, based on both the nature of the material and the quantity evolved, then becomes: roc--c . ct By comparing values of cjct for different decomposition products evolved under one set of conditions, toxicity from each product could be assessed. In order to present data on toxicity in a consistent manner the authors suggest using the equation: /=-- er where c0 is the concentration of a volatile or gaseous product evolved when one grant of original material is decomposed and the decomposition products are diffused in a volume of 1 ms, and ct is the concentration of gases lethal to man after 30 min. Toxicity, based on the above equation, was determined for the analytical results obtained in the current investigation and presented in Table 11, The main decomposition product of PVC was hydrogen chloride. The toxicity due to that product was found to be three to ten times as great as that due to carbon monoxide when PVC was decomposed in the presence of air. Even if it were possible to convert all the carbon of PVC to carbon monoxide the degree of toxicity (based on the present method of evaluation) due to hydrogen chloride would be twice as great as that due to carbon monoxide. The toxicity due to the decomposition products of different polymers can also be evaluated if, as a first approximation, synergism is neglected and it is assumed that the combined effect of toxicity is additive. The data for PVC are also given in Table II. The toxicity due to decomposition under different experimental conditions could also be studied using method of evaluation by varying temperature, samp ratio, etc. The authors realise the limitations of the proposed met of evaluation. Toxicities arc not necessarily additive, an mechanisms of the toxicity for hydrogen chloride and ca monoxide are quite different. The most serious effee hydrogen chloride arc on the eyes or respiratory tract, toxic effect of carbon monoxide is due primarily to its a!i for haemoglobin, and this could lead to damage of the b Synergistic effects between different conditions, e.g., heat carbon monoxide concentration, and oxygen depletion carbon monoxide, were neglected because the present sta knowledge on this subject precludes consideration i simple formula. In spite of these limitations, the prop methods of evaluation should be of value, especially in design of animal experiments to obtain data on toxicity. Acknowledgment This paper is a contribution from the Division of Bui! Research, 'National Research Council, Canada, and is i lished with the approval of the Director of the Division. Fire Research Section, Division of Building Research, National Research Council, Ottawa, Canada Received 22 February, 196 amended manuscript, J 6 June, 19( References 1 Coleman, E. H., & Thomas, C. H., J. appl. Chem., Bond., V 4, 379 2 Schriesheim, A., J. Res. natn. Bur. Stand., 1956, 57, (4), 245 2 Strombcrg, R. R., Straus, S, & Achhammer, U. G,, J. Pol Set., 1959, 35, 355 Gilbert, J. B,, & Kipling, J. J., Fuel, Load., 1962, 41, 249 5 Kaiser, R., `Gas Phase Chromatography, Vol. 111. Tables Gas Chromatography', 1963, p. 101 (.London: Butterwort. * Threshold Limit Values for 1965, American Conference Governmental Industrial Hygienists 7 Fieldner, A. C.. Katz, S. H., & Kinney, S. P., U.S. Bur. ,\fii tech. Pap. 248, 1921, p. 58 Jacobs, M. B., `Analytical Chemistry of Industrial Poiso Hazards and Solvents,' 1949, p,788 (New York: Intcrscien OLI 7358 J. ftppl* Client., 1967, Vol. 17, Deccml