Size Distribution Of Smoke Particles Research Articles

High-frequency electric knife smoke particles: An experimental study on factors influencing emission characteristics

During surgery, the use of a high-frequency electric knife produces smoke, which can be harmful to the health of indoor medical staff and patients. The quantity and particle size distribution of smoke particles produced by different tissues may vary. Understanding the release characteristics of these smoke particles is necessary to clarify their impact on the surgical environment and to seek effective smoke control methods. A previous comparative analysis of human and pig tissues revealed that they share similar water and fat compositions in certain anatomical regions. In this study, we investigated the emission characteristics of smoke particles from various tissues of pigs (skeletal muscle, liver, kidney, skin, and subcutaneous fat) under different operating powers of an electric knife. We measured the indoor particle number concentration (particle concentration), and estimated the PM2.5 mass concentration (PM2.5 concentration), particle size distribution, and emission rate of the smoke particles. The study obtained the particle emission rates of different tissues under different electric knife operating powers, results of which showed that (1) during the operation of the electric knife, mainly small particles below 1 μm are produced. Among them, particles of 0.3 μm were the most abundant, with a particle concentration level of up to 109 particles/m3, accounting for 85.17–97.64% of the total particle number, and as the particle size increased, the particle concentration and percentage decreased significantly. (2) The water and fat compositions of different tissues influenced the indoor particle concentration and emission rate of the smoke emitted by the electric knife. Among different tissues, subcutaneous fat tissue had the lowest particle concentration and emission rate. (3) The electric knife operating power mainly affected particles below 1 μm, and except for kidney tissue, the indoor concentration and emission rate of these particle sizes were positively correlated with the power. The experimental results can provide data reference for the use of high-frequency electric knives in surgeries involving different human tissues in the operating room.

Far-field signature of fire in low gravity: Influence of ambient oxygen content and pressure on size distribution of smoke particles

Fire detection in space habitats is hindered by the unique characteristics of smoke particles released by weakly buoyant flames. For the first time, non-invasive measurements of particle concentration, size, and light absorption properties are performed in the downstream flow of a flame spreading in microgravity. The studied flame spreads over Low Density PolyEthylene (LDPE) coated Nickel/Chrome (NiCr) wires in an opposed oxidizer flow. The far-field signature can then be contrasted with previous measurements performed over the same configurations and related to the morphology of soot particles sampled in and behind the flame.Following measurements regarding the impact of gravity, the influence of ambient pressure and oxygen content on the characteristics of the particles is reported in microgravity. Increased pressure boosts the soot production rate, leading to higher concentration levels of particles detected for any class of particle size. Higher pressure also causes larger aggregates that exhibit a higher level of polydispersity among the constituting primary particles. This tends to enhance light absorption, more specifically at larger particle size. Less intuitively, increased oxygen content accelerates the pyrolysis rate, therefore hastening soot particles’ maturity, and ultimately increasing the detected soot concentration. In addition, enhanced oxygen content reduces organic carbon within particles, boosting light absorption regardless of the particle size. The far-field signature and its sensitivity to the ambient conditions are in decent agreement with observations of soot particles collected at the trailing edge of the flame. As a result, combining higher oxygen content and lower pressure in future space habitats as projected by the main space agencies can cancel out the effect on the detection threshold of a given flame if this threshold only includes the concentration level.

Measurement of the Size Distribution of Smoke Particles through Direct Sampling at the Exit of a Steady-State Tube Furnace

The size distribution of smoke particles, influenced by varying fire conditions, constitutes a significant research focus in the firefighting domain concerning fire detection and the impact on lung deposition which is a major contributor to both short- and long-term casualties among residents and firefighters. Currently, the ISO/TS 19700 method is commonly employed to measure characteristics of combustion products, including composition and concentration, primarily for gaseous substances. However, due to measurement challenges, limited research results exist on particulate substances using this method, and outcomes vary significantly among researchers. The particle size distribution which is the typical characteristics of particulate materials is crucial factor leading to discrepancies in measurements at the combustion furnace outlet. This distortion is influenced by factors such as particle collision, temperature changes, and residence time in the mixing chamber installed for cooling and dilution. This study unveils the disparity in particle size distribution between using a mixing chamber and direct sampling. A solution is proposed by replacing the mixing chamber at the outlet of the steady-state tube furnace specified in the existing ISO/TS 19700 method with a direct sampling approach. Smoke particles generated under combustion conditions at various temperatures and equivalence ratios were directly sampled at the furnace exit. These samples underwent a two-stage dilution process, and the real-time particle size distribution was measured using an electrostatic low-pressure impactor. This approach minimizes distortion of the particle size distribution attributable to the mixing chamber.

Transmission Characteristics of Terahertz Imaging Detection in Smoke Environments

The terahertz imaging detection technology is applied to low-visibility fire environments to improve the traditional imaging detection equipment affected by the changes in the morphology and particle size distribution of smoke particles. This study focus on the transmission characteristics of terahertz waves in fire and smoke environments. A model for the propagation of terahertz waves is obtained. Terahertz imaging equipment is used to experimentally investigate the flue gas environment generated by three standard fires and combined with numerical simulations to analyze the influence of the terahertz wave transmission under different flue gas environments. The results show that the transmission of terahertz waves in a flue gas environment is affected by factors such as the smoke particle size and flue gas concentration; however, the transmission is significantly better than that obtained with traditional detection methods. In standard fire experiments, the terahertz equipment can achieve good imaging results, and the transmittance of terahertz waves is maintained above 88%.

Prediction of Size Distribution and Mass Concentration of Smoke Particles on Moisture Content and Combustion Period from Para Rubber Wood Burning

The size distribution and total particle mass concentration (TPMC) of smoke particles from para rubber wood (Hevea brasiliensis) combustion in the ribbed smoked sheet (RSS) process were studied. In this experiment, temperature data values of para rubber wood combustion were recorded at 500 mm above the base of the fire by K-type thermocouples. The wood moisture content and wood combustion period were used to find and improve an equation of smoke particle size distribution (SPSD) and TPMC by the response surface method (RSM). An eight-stage Andersen air sampler and a high-volume sampler were used to measure and calculate SPSD and TPMC, respectively. Resulting data in this experiment showed that TPMC ranged from 3.12 to 77.42 mg/m3. SPSD was single mode in which MMAD, mass median aerodynamic diameter, ranged from 0.64 to 1.27 microns for para wood with moisture content ranging from 31.5 to 89.7% dry weight basis. The combustion period and moisture content of para wood have a direct effect on the change of temperature data above the base of the fire and the TPMC and MMAD values. For predicting TPMC and MMAD values by the para wood moisture contents in each combustion period, the results found that the second-degree model was a better plot than the first-degree model, confirmed by higher values of the coefficient of determination (R2).

Measurement of the Size Distribution of Smoke Particles with Plastic Types Under Various Fire Conditions

Measurement of the Size Distribution of Smoke Particles with Plastic Types Under Various Fire Conditions

The Influence of Currents on the Ignition and Correlative Smoke Productions for PVC-Insulated Electrical Wires

Ignition of energized polyvinyl chloride insulated copper conductor wires by external heating was investigated for a better understanding of the initiation of electrical wire fires. First, a simplified theoretical analysis was developed to quantitatively explain the effects of currents on the ignition of electrical wires. The numerical result predicted that the ignition time concavely decreases with the increasing external heat flux while convexly decreasing with the increasing current of wire. Second, experiments with several sample wires were conducted to study the ignition process. It showed a good consistency between the experimental and numerical results. Using the methods of Transmission Electron Microscope, Scanning Electron Microscope and Fast Particulate Spectrometer, the properties of released smoke productions were obtained. The smoke particles size distribution was found independent to the current of wire and showed the same morphology with the standard test fires. The properties of pyrolysis smoke particles showed a two-regime behavior with the increasing current of wire. The pyrolysis smoke particle size distribution with one certain current showed a bimodal phenomenon. The three-stage changes of the count median diameter and geometry mean diameter were also presented.

Study on the real-time size distribution of smoke particles for each fire stage by using a steady-state tube furnace method

For the analysis of the adverse effects of smoke on health, it is essential to determine the amount and location of smoke particles deposited in the respiratory tract. However, the deposition characteristics of the particles are influenced by their morphology and size distribution. Moreover, the real-time particle size distribution during inhalation is important for determining smoke particle deposition in the lungs. Smoke particles generated under different fire conditions differ in their physical and chemical characteristics. Thus, there is a need to adopt international standard methods for characterizing the particles generated in fire. In the present study, the size distributions together with morphology of smoke particles were measured for each fire stage by using the steady-state tube furnace method given in ISO/TS 19700. The size distributions of smoke particles from wood and polypropylene (PP) were measured in real time by using an electric low-pressure impactor (ELPI+), and their morphologies were analyzed using transmission electron microscopy (TEM).

등속공급 튜브연소로를 이용한 각 연소조건에서의 연기입자 형상 분석

화재현장에서 발생하는 연기는 일반적으로 연소가스와 더불어 여러 가지 성분의 유기증기 및 미연탄소로부터 생성된 미세입자로 되어 있다. 연기는 호흡기로 흡입되어 장단기 인체피해를 유발한다. 화재 시 발생하는 유독가스나 입자에 의한 피해를 예측하기 위해서는 연기입자의 호흡기관 내 이송과 침전, 그리고 입자를 매개로 한 유독가스의 흡수와 흡착등의 현상 파악이 필수적이며 이에 연기입자의 크기 및 형상은 이와 같은 현상의 변화에 중요한 변수로서 작용한다. 이 연구에서는 화재 시 발생하는 연기입자의 흡입에 의한 인체피해 특성을 예측하기 위하여 가연물 및 화재 조건에 따른 연기입자의 크기 및 형상에 대한 분석을 수행하였다. 국제표준에 따른 연소생성물 분석을 위하여 ISO/TS 19700 기준에 따라서 등속연소로를 제작하고 각 가연물에 대하여 연소로 온도 및 당량비 조건으로 정해지는 4가지 대표적인 화재조건, 즉, 저온불완전연소, 완전불꽃연소, 불완전불꽃연소, 고온불완전연소 조건에서 연기입자를 발생시켰다. 발생된 연기입자는 다단 충돌집진기를 이용하여 채집한 다음 투과전자현미경으로 크기 및 형상을 분석하였다. Smoke from fire is a mixture of combustion gases and particles which include micro-droplets formed from condensed organic vapors and carbonaceous agglomerates. The inhalation of smoke particles causes adverse health effects, and it is prerequisite for the hazard and risk analysis of the smoke particles to know how they behaviour in the respiratory tract. The characteristics of the absorption and adsorption of toxic gases and the amount and location of the particle deposition within the respiratory tract that determine the adverse health effects are related to the morphology and the size distribution of smoke particles. In the present work, as a preliminary study for the adverse health effects of smoke particles, the morphologies of the smoke particles from combustible materials were investigated for each fire stage: smouldering, well-ventilated flaming, small under-ventilated flaming, fully-developed under-ventilated fire. The steady-state tube furnace method given in ISO/TS 19700 was used for the generation of smoke particles. The fire stages were controlled by changing furnace temperature and equivalent ratio. The morphologies were analyzed by using Transmission Electron Microscope (Bio-TEM) by collecting the particles on TEM grids put on each stage of a cascade impactor.

Effects of Environment Temperature and Humidity on Size Distribution of Smolder Microparticles

The smoke particle size distribution of cotton rope smoldering fire were measured with DMS500 Fast Particulate Spectrometer under different temperature and humidity. Through the experiments, we prove that the temperature and humidity of environment have a great influence on cotton rope smoldering smoke particle size distribution. Cotton rope smoldering smoke particle size distribution at an elevated temperature will migrate to small size. Nevertheless, the effect of humidity is more complicated that need a more depth research. Additionally, Fire smoke aerosol is a non-steady-state.

Analysis of Dust Properties to Solve the Complex Problem of Non-fire Sensitivity Testing of Optical Smoke Detectors

The purpose of an automatic fire detection system is the fast and reliable detection of arising fires in order to keep damage as low as possible. The European Standard EN54 defines a series of tests to prove and certify the functionality of smoke detectors, i.e. to prove that the detector is able to detect a fire in a prescribed period of time. Unfortunately the complex task of avoiding false alarms is not completely addressed. In contrast to the well standardized methods for the evaluation of the detection capability of a smoke detector, there is a lack of a reproducible and representative test method concerning the false alarm susceptibility with regard to nuisance aerosols. The consequences of false alarms should not be underestimated, as they may cause costs to serve the operator, especially in airborne applications. Many false alarms are caused by construction works in the surrounding of smoke detectors. For that reason several dust sources have been analyzed. Several approaches are possible and have been implemented to reduce the false alarm susceptibility of optical smoke detectors caused by dust and steam, e.g. different wavelengths and scattering angles. Unfortunately the developer has no representative test methods to quantify improvements and to point out the false-alarm resistance with e.g. a seal of quality due to new developments. Important is the knowledge of dust and steam properties such as the particle size distribution in comparison to particle size distribution of smoke of a fire. This paper presents a new approach for the test of smoke detectors regarding their susceptibility to false alarms due to nuisance aerosols, like steam and dust. The presented test apparatus is a very helpful and important tool for developers as well as for test houses during the developing and certification process. System designer will have a quantitative decision criterion to find the optimal detector for a specific place of installation. The paper compares the analysis of dust properties caused by construction works with standardized test dusts and shows how to solve the problem.

결절법을 이용한 전영역에서의 연기입자 응집체에 대한 브라운응집현상 해석

The size distributions of smoke particles from fire are prerequisite for the studies on fire detection and adverse health effects. Above the flame of the fire, coagulation dominates and the smoke particles grow from 1 to 50 nm up to 100 to 3,000 nm, sizes ranging from the free-molecular regime to the continuum regime. The characteristics of the agglomeration of the smoke particles are well known, independently for each of the free-molecular and continuum regimes. However, there are not many systematic studies in the entire regime by the complexity of the mechanisms. The purpose of this work is to find the characteristics of the development of the size distribution of smoke particles by agglomeration in the entire size range covering the free-molecular regime, via transition regime, to the near-continuum and continuum regime for each variation of parameters such as fractal dimension, primary particle size and dimensionless coagulation time. In this work, the dynamic equation for the discrete-size spectrum of the particles was solved using a nodal method based on the modification of a sectional method. In the calculation, the collision frequency function for the entire regime, which is derived by using the concept of collision volume and general enhancement function, was applied. The self-preserving size distribution for the entire regime is compared with the ones for the free-molecular or continuum regimes for each variation of the parameters.

Development of the size distribution of smoke particles in a compartment fire

Smoke affects fire detection and visibility as well as the number of fire victims through inhalation. The size distributions of smoke particles are prerequisites for understanding the characteristics of fire smoke. The purpose of this work is to find the characteristics for the development of the size distribution of smoke particles in a compartment fire. In this work, the dynamic equation for the discrete-size spectrum of particles was solved using the nodal method. The collision frequency function for the entire regime, reflecting the fractal dimension of the particles, was applied. The results were presented for each variation of the parameters such as the history of the heat release rate, smoke yield, and the size of primary particles.

Optical-microphysical properties of mixed smokes from a few spatially separated sources

A series of experiments is performed to study the specific features of formation of the mixed-composition smokes from a few spatially separated sources of thermal decomposition of various types of wood material. It is shown that, in order to make an adequate prediction of the optical properties of the smoke aerosols, it is necessary to take into account not only the complex inhomogeneous structure of the disperse composition (the smoke particle size distribution density s(r)), but also variations in the complex refractive index (CRI) m = n − iχ over the smoke particle-size spectrum. Mixing the products of thermal decomposition of combustible forest materials generates smoke, consisting primarily of two aerosol components separated on the size scale: the finely dispersed component ( 300 nm) with the imaginary part χ ∼ 0.005–0.08. It is shown that the effective average n and χ values over the size range increase not due to external mixing of disperse components, but rather to penetration of the finely dispersed absorbing component into the structure of particles of other size ranges.

Effects of Moisture Content and Burning Period on Concentration of Smoke Particles and Particle-Bound Polycyclic Aromatic Hydrocarbons from Rubber-Wood Combustion

Physical and chemical characteristics of particles from rubber-wood combustion in a natural rubber sheet smoking process were studied. Experimental parameters include wood moisture content and wood-burning period. The size distribution of smoke particles was measured by using an 8-stage Andersen air sampler. Total smoke particle concentration was determined by collecting particles using a modified high volume sampler. Polycyclic Aromatic Hydrocarbons (PAHs) were extracted with Benzene-Ethanol by using ultrasonic technique and analyzed by HPLC/UV detection. Results show that the size distribution of smoke particles is single-mode in which the mass median aerodynamic diameter (MMAD) is 0.68 μm and the average smoke concentration is 15.806 mg/m3. This is equivalent to a mass emission to workplace of 4.33 kg/month/room. The smoke particle concentration and associated PAH concentration clearly depend on the wood moisture content and burning period. The highest PAH concentration and smoke particle concentrations were found to be 60.59 to 118.06 μg/m3 and 23.35 to 47.54 mg/m3, respectively, for a wood moisture content of 37.4 to 73.6% d.b. (dry basis) at the initial period. Smoke particle-bound PAHs are dominated by 4-6 ring PAH compounds that contribute to more than 60% of the total PAHs.

Tobacco industry research and efforts to manipulate smoke particle size: Implications for product regulation

Over the past half-century of cigarette design, tobacco manufacturers have prioritized efficiency of delivery alongside ease of inhalation and use. As a result, the modern cigarette is uniquely effective at facilitating the absorption of nicotine as well as carcinogens and other toxins. The present study draws on internal tobacco company documents to assess industry consideration of the role of smoke particle size as a potentially controllable influence over inhalation patterns and lung exposure. Tobacco manufacturers evaluated particle size manipulation both as a means of controlling physical and sensory product attributes and as a possible approach to reducing health hazards related to exposure. Industry scientists concluded that the smoke aerosol particle distribution of conventional cigarettes, constructed within common parameters, falls within a narrow and effective inhalation range. However, the internal findings suggest that differences in smoke particle size distribution are possible through less conventional approaches to product design. We propose that particle size be included among the many design features to be considered in emerging tobacco product regulation. However, the present review does not address whether particle size regulation would be a plausible means of substantially reducing addictiveness or harmfulness of cigarettes, and therefore we do not propose it as a high-priority target for regulation.

Measurement of Smoke Particle Size and Distribution Within a Gas Turbine Combustor

The objective of the work described in this paper was to identify a method of making measurements of the smoke particle size distribution within the sector of a gas turbine combustor, using a scanning mobility particle sizing (SMPS) analyzer. As well as gaining a better understanding of the combustion process, the principal reasons for gathering these data was so that they could be used as validation for computational fluid dynamic and chemical kinetic models. Smoke mass and gaseous emission measurements were also made simultaneously. A “water cooled,” gas sampling probe was utilized to perform the measurements at realistic operating conditions within a generic gas turbine combustor sector. Such measurements had not been previously performed and consequently initial work was undertaken to gain confidence in the experimental configuration. During this investigation, a limited amount of data were acquired from three axial planes within the combustor. The total number of test points measured were 45. Plots of the data are presented in two-dimensional contour format at specific axial locations in addition to axial plots to show trends from the primary zone to the exit of the combustor. Contour plots of smoke particle size show that regions of high smoke number concentration once formed in zones close to the fuel injector persist in a similar spatial location further downstream. Axial trends indicate that the average smoke particle size and number concentration diminishes as a function of distance from the fuel injector. From a technical perspective, the analytical techniques used proved to be robust. As expected, making measurements close to the fuel injector proved to be difficult. This was because the quantity of smoke in the region was greater than 1000mg/m3. It was found necessary to dilute the sample prior to the determination of the particle number concentration using SMPS. The issues associated with SMPS dilution are discussed.

The influence of combustion-derived pollutants on limestone deterioration: 1. The dry deposition of pollutant gases

This study concerns quantification of the relative chemical degradation effects of dry deposition of combustion-derived atmospheric pollutants, HCl, SO 2 and NO 2, on Portland and Monks Park limestones, employing laboratory exposure chambers for periods of 30 days. Using presentation rates up to 40 × 10 −4 μgcm −2s −1, the pollutants were assessed individually and in various combinations, along with ozone as oxidant, at 84% RH with dry or water-wetted surfaces. The degradation was followed by analysis of exposed stone, for Cl −, SO 4 2− and NO 3 −, and of run-off solution for Ca 2+, in addition to the anions. From these data, the total calcium released from limestone to reaction ions and products and the percentages of each pollutant reacted (and so the deposition velocity ( V D)) in each exposure regime were calculated. HCl acted independently of the presence of other pollutants, showed 40 and 100% reaction (mass transport control) and V D values of 2.2 and 5.3 mm s −1, at 84% RH and on wetted surfaces, respectively. The reactivity of SO 2 rose from 2.5 to 35%, and V D from 1 to 2.9 mm s −1, from conditions of 84% RH to those with the presence of water, NO 2 and O 3. Similarly, the reactivity of NO 2 rose from 3 to 40% at 84% RH in the presence of SO 2 and O 3, with a V D at 3 mm s −1, but decreased in the presence of run-off solution. A limited study was performed on smoke-coated and naturally exposed, reaction-product-coated, samples. In addition to obvious factors such as deposited mass, chemical constitution and transfer, smoke particle size distribution should also be considered in any possible action on limestone. Concerning naturally exposed samples, non-wetted surface reaction products tended to reduce the attack of pollutants, but had no resisting effect when wetted.

Risk-based spacecraft fire safety experiments

This paper utilizes the scenario approach of risk assessment to identify modeling needs and, in turn, experiments that would aid in the development of models that would meet these needs. Due to the closed environment of a spacecraft and the lack of egress, fire on-board may pose a severe problem. There are many differences between a fire on-board the spacecraft and one in a terrestrial facility and they must be accounted for in the assessment of risk. Both the risk assessment methodology and the phenomena-based models must be modified. This paper discusses some of the methodology modifications, as well as special experimental results. Multiple experiments have been conducted in terrestrial and microgravity environments in order to construct and validate models required for the assessment and management of risk on-board spacecraft. A logic diagram analyzing the ways in which the crew may be injured and/or the spacecraft may be damaged, as well as operating experience, have identified wire overheating events as being potentially significant accident initiators. As a result, the experiments have concentrated on quantifying the pyrolysis event of a wire being overheated with excessive current. A preliminary set of experiments at the 2·2-second NASA Lewis Drop Tower has led to several observations. The event is violent due to the high heating rates. At these high heating rates, a jet of hot gases and smoke was observed. Frequently the conductor would melt down, sometimes ejecting molten pieces of the copper conductor. The event poses a threat to targets in the near vicinity and further away. Also, the smoke particle size distribution is shifted towards larger sizes in a microgravity environment. This may prove very important in designing a smoke detector. While significant results were obtained from these tests, longer durations of microgravity are required for further quantification to be possible.

Experimental Needs For Spacecraft Risk Assessment

Due to the closed environment of a spacecraft and the lack of egress, fire on-board may pose a significant risk. There are many differences between a fire on-board the spacecraft and one in a terrestrial facility that must be accounted for in any risk assessment. Both the risk assessment methodology and the phenomena-based models for terrestrial applications must be modified. This paper discusses some of the methodology modifications, as well as several experimental results. Multiple experiments have been conducted in terrestrial and microgravity environments in order to construct and validate models required for the assessment and management of risk on-board spacecraft. Past Shuttle experience with electrical overheating events supports the belief that these types of events may pose a serious threat to any human-crewed spacecraft and/or the crew. Experiments have been performed to simulate these events and quantify several damage modes. A preliminary set of experiments at the 2.2 second NASA Lewis Drop Tower has led to several conclusions. First, the production of damage causing elements depends on temperature. Second, the wire insulation involved can have a significant impact on the risk of the event. Third, the smoke particle size distribution is shifted towards larger sizes in microgravity, which may prove important in designing a smoke detector or selecting a sensitivity.