Smoke Gases Research Articles

Transformation of reactive PAH on particles by exposure to oxidized nitrogen compounds and ozone

In order to study the conditions for atmospheric transformation of reactive polycyclic aromatic hydrocarbons (PAH) on particles by exposure to nitrogen dioxide (NO 2), nitrous acid (HNO 2), nitric acid (HNO 3) and ozone (O 3), a set of experiments has been carried out in a flow reactor. Soot and PAH were generated in a smoke gas generator and collected on a glass fiber filter. The filter was attached to the Teflon coated wall in the reactor tube and the reactive gas was added to the purified and humidified air pumped through the reactor. After exposure, the filter was soxhlet-extracted with methylene chloride or acetone and fractionated on a silica gel column into five fractions with increasing polarity. The results indicate that reactive PAH are transformed when exposed to NO 2 and O 3, while HNO 2 and HNO 3 have no effect. The decrease of the concentration of PAH is dependent on the NO 2 and O 3 concentration, the time of exposure, and the relative humidity. The presence of hydrochloric acid (HCl) or sulphur trioxide (SO 3) increased the reactivity. So far, only a few transformation products have been identified. The formation of oxy derivatives and above all, even more polar compounds are dominating. Only when SO 3 is introduced during the generation of PAH/soot, the formation of nitron derivatives is favoured.

Detection of smoke gases by solid state sensors — A focus on research activities

Conventional smoke detection in fire alarm systems is based on a measurement of either physical properties of smoke aerosols (ionization and optical detectors), temperature increase (thermal detectors) or electromagnetic radiation emitted by the fire (radiation detectors). Not much emphasis has been put on smoke gases as signatures of various types of fires. In this paper the most elementary gases produced in CEN-norm fires are qualitatively discussed in order to define levels of gas concentrations reached on time scales typical of early fire warning. Based on that information, various principles and the current state of the research and development of solid state gas sensors are presented and discussed. These are, in particular, the solid state electrolyte, the metal oxide semiconductor, the silicon semiconductor device element and, finally, the microcalorimeter. It is concluded that, with the exception of the last mentioned operating principle, solid state gas detection could provide a viable alternative or additional means for the detection of smouldering or pyrolytic fires at an early stage.

Analysis and evaluation of carcinogenic polycyclic aromatic hydrocarbons from the view of food hygiene and toxicology--a survey

The contamination of foods is technologically induced by smoke gases (smoking, grilling, drying) and also due to environmental factors such as air and soil, soil conditioners, migration from plastics etc. The author presents and discusses the major problems concerning the accurate analysis of smallest amounts (micrograms/kg of food) of polycyclic aromatic hydrocarbons (PAH). Such problems occur in the separation from he matrix and the clean-up of the PAH, as well as in their identification and determination. Benzo[a]pyrene - under certain preconditions internationally accepted as the reference standard of PAH - is ingested by the GDR citizens in an order of magnitude ranging from 0.2 to 1.0 mg per annum; this corresponds to a daily intake varying within 0.5 and 2.5 micrograms. It is particularly difficult and as yet not possible to establish scientifically founded maximum tolerances for cancerogenic substances in foods which exclude a risk to man. The establishment of tolerances in the sense of a "socially acceptable level of risk" (which does not mean physiological safety) is recommended. Controlled tolerances would enable the legislator to aim at the optimum reduction or exclusion of the cancerogenic noxious agent in the framework of technical and economic possibilities.

Transformation of polycyclic aromatic hydrocarbons during sampling.

Individual PAH are shown to undergo chemical transformation when exposed to gases such as NO2, O3 and SO3. The possibility of artifact formation during sampling in stacks and in ambient air is discussed. PAH on soot, formed in a smoke gas generator, and exposed to NO chi and SO chi in a thermostated oven were degraded as a result of the sampling technique. Addition of NO2 (1 ppm) or gaseous HNO3 (120 ppb) during ambient air sampling caused degradation of individual PAH on particles and formation of the corresponding mononitro-PAH. Addition of 200 ppb O3 or 100 ppb gaseous HNO2 had no detectable effect. Thus, artifact formation can occur as a result of the presence of NO2, HNO3, or SO chi both in stack gas sampling and in sampling of PAH on particles in ambient air.

Transformation of Polycyclic Aromatic Hydrocarbons during Sampling

Individual PAH are shown to undergo chemical transformation when exposed to gases such as NO2, O3 and SO3. The possibility of artifact formation during sampling in stacks and in ambient air is discussed. PAH on soot, formed in a smoke gas generator, and exposed to NO chi and SO chi in a thermostated oven were degraded as a result of the sampling technique. Addition of NO2 (1 ppm) or gaseous HNO3 (120 ppb) during ambient air sampling caused degradation of individual PAH on particles and formation of the corresponding mononitro-PAH. Addition of 200 ppb O3 or 100 ppb gaseous HNO2 had no detectable effect. Thus, artifact formation can occur as a result of the presence of NO2, HNO3, or SO chi both in stack gas sampling and in sampling of PAH on particles in ambient air.

Smoke and Toxic Gas Production from Burning Polymers

Abstract This paper describes current studies at the Fire Research Station on the role of smoke and toxic gases in causing injury and death in fires involving polymeric materials used within the structure and contents of buildings. The work involves obscurational studies of smoke, chemical analysis of decomposition and combustion products, pathological studies and, where appropriate, bioassay procedures. Basic details of these studies are presented together with a summary of the work carried out, and conclusions reached, following the fire at the Woolworth's store, Manchester, on 8 May 1979, in which 10 persons lost their lives. This event focused attention in the United Kingdom on the rapid release of smoke and toxic gases from burning furniture and furnishings.

Computation of fire induced flow and smoke coagulation

Mathematical models for the calculation of the dynamics of smoke and hot gases induced by enclosure fires are presented. The models predict the evolution of the size distribution of smoke aerosol under the influence of coagulation, as well as the large scale fluid motion and temperature fields. The calculations contair three main ingredients: a finite difference solution of a hydrodynamics problem, the computer evaluation of an exact solution to the aerosol coagulation equation, and a Lagrangian particle tracking scheme to imbed the coagulation dynamics in the hydrodynamics. The hydrodynamics model is a time dependent variable density, two dimensional, infinite Grashof number flow driven by a prescribed heat source. No turbulence model is employed; the large scale eddy motion is calculated directly from the equations of motion. The mathematical particles each represent a large ensemble of aerosol particles, distributed initially in size according to the experimentally observed Junge distribution. They are introduced into the spatial grid in a random fashion near the heat source. The subsequent evolution of the size distribution in space and time is calculated deterministically from the solution to the Smoluchowski equation for the size distribution and the Lagrangian equations of motion for the spatial coordinates. Sample results of the hydrodynamic and aerosol properties are presented. Comparisons between calculations and relevant experiments are shown.

Finite Difference Calculations of Buoyant Convection in an Enclosure, I. The Basic Algorithm

A novel mathematical model of buoyant convection in an enclosure, developed earlier, is solved by finite difference techniques in the two-dimensional case. This model has been developed as a principal analytical tool for the prediction of the movement of smoke and hot gases in fires. Effects of large density variations caused by substantial heating are retained while acoustic (high-frequency) waves, which are unimportant to buoyant convection, are analytically filtered out. No viscous or thermal conduction effects are included in the model. These two characteristics (filtering and lack of dissipative effects) distinguish the model from all others describing buoyant convection. The mathematical model consists of a mixed hyperbolic and elliptic set of nonlinear partial differential equations: the problem is a mixed initial, boundary value one. An explicit time-marching algorithm, second-order accurate in both space and time, is used to solve the equations. The computational procedure uses a software package for solving a nonseparable elliptic equation developed especially for this problem. The finite difference solutions have been carefully compared with analytical solutions obtained in special cases to determine the stability and accuracy of the numerical solutions. The computer model has been used to compute the buoyant convection produced in an enclosure by a spatially distributed heat source simulating a fire. The computed results show qualitative agreement with experimentally observed buoyant convection in enclosure fires.

The Manchester Woolworth's store fire, May 1979: Burning characteristics of the furniture

This paper describes a fire test carried out by the Fire Research Station for the Greater Manchester Fire Service to study the development of fire in stacked furniture in connection with the fire which occured in the store on 8 May, 1979 in which ten persons lost their lives. The work has shown that the upholstered furniture (polypropylene fabric over poly-urethane foam) in a mixed stack, representing as nearly as possible that of the store, gave a very rapid development of fire with sufficient quantities of smoke and toxic gases to have made escape very uncertain from the floor of origin of the fire from two minutes after detection of the fire.

The Problems, Language and Scientific Basis of Flammability Testing

Flammability tests are intended to provide a measure of the fire hazard of a material or product. The gross factors involved are the ease of ignition, the rapidity of combustion development, the severity of conditions produced by the combustion (heat, smoke and toxic gas loads), and the performance of a product under a fire load. Most flammability tests have been developed by practical people under external pressures (legal or corporate) to produce a believable, reproducible test requiring a minimum of effort, equipment, and manpower. The scientific understanding of the tests is a luxury usually denied the designers. The resulting tests each measure some aspect of flammability, usually reproducible and well. However, because of thtlack of basic understanding, related tests measure different aspects of flammability and correlate poorly. There is a need for increased effort in understanding tests scientifically to aid in correlating and interpreting the results. A side result of this situation is that a jargon has developed which often obscures the usage and basis of the tests. This paper will document the chaotic state of flammability testing, define some of the specialized terms, and close with some suggestions for the scientific interpretation of some aspects of wire and cable testing as an example of the approach which the author feels would increase understanding in this field.

Untersuchungen von Sedimentkernen des Bodensees I. Profile der polycyclischen aromatischen Kohlenwasserstoffe / Investigation on Drilling Cores of Sediments of Lake Constance I. Profiles of the Polycyclic Aromatic Hydrocarbons

Abstract The content of polycyclic aromatic hydrocarbons (PAH) from sediment layers of Bodensee areas differently exposed to environmental burden were determined. 32 PAH and 10 nitrogen containing PAH were identified by comparison with authentic samples. A method of quantitativ enrichment and gasdiromatographic determination of PAH containing 4-7 rings is described. In a comparative profile analysis only 20 most abundant PAH have been regarded. Low burdened areas (entre of the lake, 250m deep; Güttingen) show only 10 - 20% of the PAH content of high-burdened areas (mouth of Argen and Schüssen). The qualitative and quantitative composition of the PAH fraction (PAH-profile) from different layers of a sediment drilling core are very similar whereas profiles from different regions can be distinguished. The concentration of PAH increases from the surface to a layer with maximum burden (1965 - 1970) and then decreases to a remaining concentration (1900). From the typical PAH profile and some characteristic compounds as e.g. benzo (b) -naphtho (2,1-d) thiophan, benz (a/c) acridines, benzo (a/b/c)-carbazoles, dibenzacridines, and dibenzcarbazoles some potential sources as motor- car traffic, petroleum, fuel oil, and used lubricating oil can be excluded. Coal combustion smoke gas is supposed to be the main source of emission.

Age-related determinants of stress-induced weight change in mice.

25-day-old male mice showed a greater incidence of body weight loss and a late peak of plasma corticosterone elevation when exposed to tobacco smoke for 5 successive days, as compared with mice exposed to filtered smoke (gas phase) or air. 50-day-old mice had a greater incidence and magnitude of body weight loss and a late plasma corticosterone peak after 5 days of air exposure, but not with gas phase or nicotine + gas phase. Diencephalic serotonin, while higher among 25-day-old mice, did not differ as a function of the stress of confinement during exposure to the ventillatory stimulus or as a function of the different stimuli. The results suggest that weight loss and the time following stimulation at which plasma corticosterone is maximally elevated may serve as indices of stress and are consistent even when the stressor-susceptibility is age-related.

Smoke and toxicity hazards of plastics in fire.

Among fatal and non-fatal casualties in fires in buildings, the annual proportion due to smoke and toxic gas has increased threefold over a period of seventeen years; over half the total fatalities in fires are now due to this cause. This paper briefly reviews the problem of smoke and toxic gases in fires and describes investigations aimed at determining whether the introduction of non- traditional materials, principally plastics, into buildings is likely to make a significant increase in the numbers of fire casualties overcome by gas or smoke. The investigations covered the pyrolysis of plastics under laboratory conditions, large-scale fire tests in which the generation and survival of significant toxic products were monitored, and measurements of the toxicity of fire gases. Results are given for rigid PVC used as wall linings and for flexible polyurethane foam burning in bulk. It is clear that large industrial fire loads of these materials can produce an unacceptable hazard, but further work is needed before conclusions can be reached for fire loads relevant to, for example, private dwellings.

Application of release rate data to hazard load calculations

The author illustrates methods of applying heat, smoke and toxic gas release rate data to calculating fire hazard loading values.

Effects of Cigarette Smoke Components on Bronchial Clearance in the Donkey

The tracheobronchial transport of insoluble radioactive particles has been studied in the donkey to determine the effects of various levels of exposure to whole cigarette smoke, filtered cigarette smoke, and hydrogen cyanide gas. Low levels of exposure to whole cigarette smoke accelerated clearance from the distal bronchi. Intermediate levels of exposure to whole and filtered smoke and HCN gas caused generalized but transient impairment of tracheobronchial clearance. At higher exposure levels, whole cigarette smoke had twice the effectiveness of filtered smoke for causing sustained impairment of clearance.

AC reflectometry: a sensitive method of measuring smoke or reactive gas in air.

The difference in reflectance between neighbouring soiled and unsoiled regions of a filter is converted into an AC signal which is amplified, rectified and displayed on a meter. Sensitivity is limited by the noise signal given by unexposed filters. Such noise is low for membrane filters, resulting in high sensitivity to smoke or any gas capable of giving a colour reaction on a suitably treated surface. By this means the smoke and hydrogen sulphide in 'clean' air can be estimated after sampling for times of the order of ten minutes.

The Effect of Perforated Tipping Paper on the Yield of Various Smoke Components

AbstractAn investigation is described concerning the effect of tipping perforations on the yield of a variety of smoke components. The degree of ventilation covered the 20-70 % range. Tipping ventilation reduces the amount of air drawn past the cone during the puff and thereby compresses the thermaI profile of the cone. The yield of gaseous smoke components which have unique precursors is a function of time-at-temperature conditions in and near the cone and the effect on the yield differs between precursors as the amount of air flow is varied. Compounds that depend on distillation or sublimation to get into mainstream smoke are much less affected by tipping ventilation, i.e., condensation of these materials onto smoke particles becomes more efficient as the air flow past the cone is reduced and less particulate smoke is produced

Evaluation of the fire hazard of duct materials

The author reports on an evaluation program of the hazards of materials based on the rates of heat, smoke, and toxic gas release, rather than on the total quantities released.

Cigarette smoke gas phase and Paramecium survival. A method for intermittent exposure.

The effect of cigarette smoke gas phase on the survival time of Paramecium aurelia was studied with an intermittent method of exposure. This method simulated human smoking and revealed the ability of activated charcoal to reduce the toxic effect of gas phase.

Components of City Growth in Selected Latin American Countries

A detailed analysis of city growth by city size categories was made for the Latin American countries of Chile Mexico and Venezuela. These countries are among the 6 most urbanized of the region and additionally they have experienced a high rate of urbanization during the last intercensal period. The analysis of city growth--the principal factor contribution to urbanization--shows why cities are growing so rapidly and consequently why urbanization is so rapid. The study of city growth covers the last intercensal period with cities classified in 6 size categories according to their size in the 1960 census. All cities with 10000 or more inhabitants in the 1960 census were studied through the intercensal period. The analysis purpose was to determine whether internal migration had been the principal factor of city growth. A migrant factor was developed in which the estimates of the number of migrants were found by multiplying the factor by the number of migrants and their descendants born in the cities. The migrant factor was .8877 for Chile .8497 for Mexico and .8283 for Venezuela. Cities are growing rapidly in Latin American countries. Mainly in those less urbanized countries urbanization is occurring without any industrialization. In these areas the supply of services necessary in cities will cost relatively more than if the country were industrializing at the same time. Yet when some of the more urbanized countries industrialize they encounter sooner those problems related to urbanization such as air pollution and sewage because factories and industries locate very close to the largest cities without taking any precautions against smoke gases or waste. Principally Latin American cities are growing so fast because the population is reproducing at a high rate. Natural growth rates in certain cities as in the case of Chile and Venezuela are higher than in rural areas. In general the birthrate by city size category declines when the city size increases except for the intermediate category of 100-500 thousand in which case the birthrate increases in the 3 countries considered. Mortality counteracts part of the effect of the differential in birthrates and thus the growth rates are not very different between rural areas and cities. Migration from rural areas to cities the 2nd important factor in urbanization in the countries considered has been observed as following almost the same pattern. In Chile and Venezuela the lowest number of net migrants is received by the middle city size category. For Mexico the number of net migrants increases with the city size.