Smoke models

The amount of particles determine the quantity of decay products that stay in the air (equilibrium fraction, F) and the fraction of activity associated with the "unattached or ultrafine mode of the size distribution (fDot) These decay products are certainly harmful at high concentrations but we cannot yet detect the effects at normal levels because the vast majority of lung cancer death are due to smoking. Models predict that potentially 9000 lung cancer deaths per year in the United States are due to indoor radon. Methods are currently available and new methods are being developed and tested for lowering the levels of radon in indoor air. 

Fire and Smoke Models - A mathematical estimation model depicting the duration and extent of heat, flame and smoke that may be generated from the ignition of a hydrocarbon release. The results of these estimates are compared against protection mechanisms (e.g., firewater, fireproofing, etc.) afforded to the subject area to determine adequacy. 

Haley Indoor pollution by tobacco smoke Model studies on the uptake by nonsmokers im Indoor air, radon, passive smoking, particulates, and housing epidemiology Proc. 3rd Internal. Conf. Indoor Air Quality and Climate, Stockholm, Sweden, Vol. 2 (1984) 313-318. 

The vapor cloud of evaporated droplets bums like a diffusion flame in the turbulent state rather than as individual droplets. In the core of the spray, where droplets are evaporating, a rich mixture exists and soot formation occurs. Surrounding this core is a rich mixture zone where CO production is high and a flame front exists. Air entrainment completes the combustion, oxidizing CO to CO2 and burning the soot. Soot bumup releases radiant energy and controls flame emissivity. The relatively slow rate of soot burning compared with the rate of oxidation of CO and unbumed hydrocarbons leads to smoke formation. This model of a diffusion-controlled primary flame zone makes it possible to relate fuel chemistry to the behavior of fuels in combustors (7). 

FIRAC is a computer code designed to estimate radioactive and chemical source-terms as.sociaied with a fire and predict fire-induced flows and thermal and material transport within facilities, especially transport through a ventilation system. It includes a fire compartment module based on the FIRIN computer code, which calculates fuel mass loss rates and energy generation rates within the fire compartment. A second fire module, FIRAC2, based on the CFAST computer code, is in the code to model fire growth and smoke transport in multicompartment stmetures. 

This is a subroutine that calculates an evaporation rate from a pool of spilled liquid in presence of wind (ORG-40), or in still air (TP-10). It was developed by the U.S. Array for downwind hazard prediction following release from smoke munitions and chemical agents. The code calculates the evaporation rate of a liquid pool, given the physical stale variables, wind speed, and diameter of pool. ORG-40 and TP-10 models are coded as a Fortran 77 subroutine, EVAP4.FOR, in D2PC. The user s manual is Whiiacre (1987). 

Tones, W. W. and R. D, Peacock, 1994 Refinement and Experimental Verification of a Model for Fire Growth and Smoke Transport, 2nd lAFSS Meeting. 

Jones, W. W., 1994, Modeling Smoke Movement Through Compartmented Structures Journal of Fire Sciences. 

Notarianni, K. A, and W. D. Davis, 1993, Use of Computer Models to Predict Tempcraiitre and Smoke Movement in High Bay Spaces, NIST NISTIR 530. 

Peacock, R D., et al., 1993a, CFAST, The Consolidated Model of Fire Growth and Smoke Transport , NIST Technical Note 1299, NIST. 

Peacock s R. D. et. al., 1993b, Verification of a Model of Fire and Smoke Transport, Fire Safety Journal 21(2), pp. 89-129. 

Zukowski, E. and T. Kubota, 1980, Two Layer Modeling of Smoke Movement in Building Pire.s, Fire Material 4. 

A large one-sixth-scale model of the unloader hopper was selected so that flow patterns in the enclosure could be evaluated.Smoke was used to simulate the behavior of the lime dust in the enclosure. The lime drop from the clamshell was simulated by releasing coarse sand, thus modeling the flow patterns caused by the volume displacement and the air entrainment. The effects of local wind speed and direction on the enclosure were also simulated. 

Example An airflow model that has been validated for temperature differences of 15 K cannot be expected to predict smoke movement accurately in a building that is on fire with temperature differences that are 10 times larger. 

Scale-model experiments have been used to study a variety of ventilation problems as air movement in a room, air movement around a building, energy flow in a building, contaminant distribution at an operator s workplace, and smoke movement in a building on fire. The theory is discussed at a general level in the references. 

A Del Electronics, Model ESP-100A, electrostatic precipitator was used for sample collection. Cigarette smoke particles were found to give approx the same particle distribution pattern on the collection filter paper as the gunshot residue, and since the smoke stains the paper, this provided a v rapid technique for optimizing operation conditions. With a flow rate of 15cfm and a corona current of 125 uA, the residue collects primarily on a narrow band across the sample paper. Samples were collected on Whatman No 1541 filter paper which lined the inside of the sample collection tube. The presence of this paper allowed air to flow only thru the center of the tube, so particle collection was made upon the filter paper exclusively. The filter paper samples were pelletized prior to neutron activation analysis... 

Whereas smokes are often characterized by the mode of their formation, any coned suspension of particles ranging from 0.01 to about 5.0 pm can be considered a smoke. These particles, when suspended in air, reflect, scatter and absorb radiation in a complex manner. A comprehensive model of these interactions in terms of visibility under various conditions was described recently (Ref 62)... 

Subsequent studies have confirmed that the reason for this discrepancy is that the rat is able to rapidly metabolise P-carotene to retinol in the intestine, through the action of intestinal dioxygenase. In contrast humans absorb P-carotene systemically such that plasma levels of P-carotene increase to levels not found in the rodent. A more appropriate animal model is the ferret, which shows a similar metabolism to humans. High levels of plasma P-carotene in the ferret induce the cellular transcription factors c-fos and c-jun, and squamous metaplasia is seen in the lung with or without exposure to cigarette smoke (SCF, 2000). Even after the investment of all these resources it has not been possible for the EU Scientific Committee on Food to set an ADI. 

Smoking. The effects of smoking on the formation of N-nitros-amines in bacon has been investigated recently by Bharucha et al. ( ). They reported that unsmoked bacon samples generally tended to contain more N-nitrosamines, presumably because of their higher nitrite content at the time of frying. Sink and Hsu (55) showed a lowering of residual nitrite in a liquid smoke dip process for frankfurters when the pH also was lowered. The effects of smoke seem to be a combination of pH decrease and direct C-nitrosation of phenolic compounds to lower the residual nitrite in the product (56). This is an area which requires further study since certain C-nitrosophenols have been shown to catalytically transnitrosate amines in model systems (57). 

Precursors and Formation. Tobaccos used for commercial products in the U.S.A, contain between 0,5 and 2,7% alkaloids. Nicotine constitutes 85-95% of the total alkaloids (14,26,27). Important minor alkaloids are nornicotine, anatabine, anabasine, cotinine and N -formylnornicotine (Figure 6), Several of these alkaloids are secondary and tertiary amines and, as such, amenable to N-nitrosation. The N-nitrosated alkaloids identified to date in tobacco and tobacco smoke include N -nitrosonornico-tine (NNN), 4-(methylnitrosamino)-l-(3-pyridyl)-l-butanone (NNK) and N -nitrosoanatabine (NAT Figure 7). In model experiments, nitrosation of nicotine also yielded 4-(methylnitrosamino)-4-(3-pyridyl)butanal (NNA 28). 

The interaction of carotenoids with cigarette smoke has become a subject of interest since the results of the Alpha-Tocopherol Beta-Carotene Cancer Prevention Study Group 1994 (ATBC) and CARET (Omenn et al. 1996) studies were released. P-Carotene has been hypothesized to promote lung carcinogenesis by acting as a prooxidant in the smoke-exposed lung. Thus, the autoxidation of P-carotene in the presence of cigarette smoke was studied in model systems (toluene) (Baker et al. 1999). The major product was identified as 4-nitro-P-carotene, but apocarotenals and P-carotene epoxides were also encountered. 

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