Dust Gas Research Articles

Influences of methane and propane on the explosion characteristics of polymethyl methacrylate and acrylonitrile butadiene styrene dusts

AbstractPolymethyl methacrylate (PMMA) and acrylonitrile butadiene styrene copolymers (ABS) are widely applied to industrial production, with the risk of explosion mixed with combustible gas increasing gradually. A 20 L spherical explosive device was used to study the variation pattern of the explosion characteristics of four gas–dust mixtures: methane/PMMA, methane/ABS, propane/PMMA, and propane/ABS mixtures. The results showed that despite adding methane and propane, PMMA and ABS dusts within the range of minimum explosion concentration are still likely to explode. The comparative analysis shows that propane is more chemically reactive than methane and PMMA and ABS dusts mixed with propane are more dangerous than those mixed with methane. Meanwhile, it was found that as the concentration of methane and propane increases, the maximum explosion pressure Pmax, maximum explosion pressure rise rate (dP/dt)max, and explosive index K of the dusts rise as well, but the increasing trend remains steady. The single‐phase methane and propane have higher maximum explosion pressure and explosive index than the gas–dust mixture, with the lowest maximum explosion pressure and explosive index found in the single‐phase PMMA and ABS dusts. With methane and propane mixed, the explosion hazard of PMMA and ABS dusts is intensified from St1 to St3. This study reveals the explosion characteristics of PMMA and ABS dusts, providing a basis for ensuring a safe working environment, preventing and controlling explosion accidents, and reducing the destructiveness of accidents.

Streaming instability with multiple dust species – II. Turbulence and dust–gas dynamics at non-linear saturation

ABSTRACT The streaming instability is a fundamental process that can drive dust–gas dynamics and ultimately planetesimal formation in protoplanetary discs. As a linear instability, it has been shown that its growth with a distribution of dust sizes can be classified into two distinct regimes, fast- and slow-growth, depending on the dust-size distribution and the total dust-to-gas density ratio ϵ. Using numerical simulations of an unstratified disc, we bring three cases in different regimes into non-linear saturation. We find that the saturation states of the two fast-growth cases are similar to its single-species counterparts. The one with maximum dimensionless stopping time τs,max = 0.1 and ϵ = 2 drives turbulent vertical dust–gas vortices, while the other with τs,max = 2 and ϵ = 0.2 leads to radial traffic jams and filamentary structures of dust particles. The dust density distribution for the former is flat in low densities, while the one for the latter has a low-end cut-off. By contrast, the one slow-growth case results in a virtually quiescent state. Moreover, we find that in the fast-growth regime, significant dust segregation by size occurs, with large particles moving towards dense regions while small particles remain in the diffuse regions, and the mean radial drift of each dust species is appreciably altered from the (initial) drag-force equilibrium. The former effect may skew the spectral index derived from multiwavelength observations and change the initial size distribution of a pebble cloud for planetesimal formation. The latter along with turbulent diffusion may influence the radial transport and mixing of solid materials in young protoplanetary discs.

When did the initial mass function become bottom-heavy?

ABSTRACT The characteristic mass that sets the peak of the stellar initial mass function (IMF) is closely linked to the thermodynamic behaviour of interstellar gas, which controls how gas fragments as it collapses under gravity. As the Universe has grown in metal abundance over cosmic time, this thermodynamic behaviour has evolved from a primordial regime dominated by the competition between compressional heating and molecular hydrogen cooling to a modern regime where the dominant process in dense gas is protostellar radiation feedback, transmitted to the gas by dust–gas collisions. In this paper, we map out the primordial-to-modern transition by constructing a model for the thermodynamics of collapsing, dusty gas clouds at a wide range of metallicities. We show the transition from the primordial regime to the modern regime begins at metallicity $Z\sim 10^{-4} \,\rm {Z_\odot }$, passes through an intermediate stage where metal line cooling is dominant at $Z \sim 10^{-3}\, \rm {Z_{\odot }}$, and then transitions to the modern dust- and feedback-dominated regime at $Z\sim 10^{-2}\, \rm {Z_\odot }$. In low pressure environments like the Milky Way, this transition is accompanied by a dramatic change in the characteristic stellar mass, from ${\sim}50\, \rm {M_\odot }$ at $Z \sim 10^{-6}\, \rm {Z_{\odot }}$ to ${\sim}0.3\, \rm {M_\odot }$ once radiation feedback begins to dominate, which marks the appearance of the modern bottom-heavy Milky Way IMF. In the high pressure environments typical of massive elliptical galaxies, the characteristic mass for the modern, dust-dominated regime falls to ${\sim}0.1\, \rm {M_{\odot }}$, thus providing an explanation for the more bottom-heavy IMF observed in these galaxies. We conclude that metallicity is a key driver of variations in the characteristic stellar mass, and by extension, the IMF.

Dust distribution of solid and adhesive mixed dust in a granular bed filter

Granular bed filters can effectively filter adhesive dust in high-temperature flue gas. In this study, polyvinyl chloride (PVC) powder was used as adhesive dust, and the mixture of PVC and ash powder was used to simulate solid and adhesive mixed dust. The effects of gas temperature, velocity, and inlet adhesive dust mass content on dust distribution in granular bed (GBF) were discussed. Results show that the mixed dust mainly accumulates on the upper part of the granular bed, and the mass of the collected dust decreases exponentially from the upper layer to the bottom layer in the GBF. The adhesive dust content collected in each layer differs from that of the incoming dust, and their deviation varies approximately linearly along with the depth of the bed. The total dust distribution and adhesive dust content deviation are influenced by gas temperature and inlet adhesive dust content but independent of gas velocity. The correlations of dust distribution of solid and adhesive mixed dust are presented based on the experimental results.

Infrared Excesses Around Bright White Dwarfs from Gaia and unWISE. II

Abstract Infrared excesses around white dwarf stars indicate the presence of various astrophysical objects of interest, including companions and debris disks. In this second paper of a series, we present follow-up observations of infrared excess candidates from Gaia and unWISE discussed in the first paper, Paper I. We report space-based infrared photometry at 3.6 and 4.5 micron for 174 white dwarfs from the Spitzer Space Telescope and ground-based near-infrared J, H, and K photometry of 235 white dwarfs from Gemini Observatory with significant overlap between Spitzer and Gemini observations. These data are used to confirm or rule out the observed unWISE infrared excess. From the unWISE-selected candidate sample, the most promising infrared excess sample comes from both color and flux excess, which has a Spitzer confirmation rate of 95%. We also discuss a method to distinguish infrared excess caused by stellar or sub-stellar companions from potential dust disks. In total, we confirm the infrared excess around 62 white dwarfs, 10 of which are likely to be stellar companions. The remaining 52 bright white dwarfs with infrared excess beyond two microns has the potential to double the known sample of white dwarfs with dusty exoplanetary debris disks. Follow-up high-resolution spectroscopic studies of a fraction of confirmed excess white dwarfs in this sample have discovered emission from gaseous dust disks. Additional investigations will be able to expand the parameter space from which dust disks around white dwarfs are found.

Kinetics of cyclone dust flotation separation in polluting industries

This article describes the study of the kinetics of flotation separation of silicate and carbon dust phases of silicon cyclones. For research, we selected 50 samples of dust gas purification production of silicon to the Silicon situated in the city of Shelekhov of the Irkutsk region. The dust caught by bag filters can be applied as an additive in concrete, rubber products or subjected to processing for expansion of a scope of application. Silicate and carbonate phase of the cyclone dust silicon production separately represent the products in demand. The cost depends on the degree of purity, structure and particle size distribution. Describes the basic dependence of the flotation nanoscale this part of carbon and microsilica. Micro particles inherent in the formation of stable heterogeneous conglomerates. Dissimilar particles can both be introduced into the foam product and remain in the chamber reducing the quality of concentrates. To solve this problem, pulp conditioning is used with the help of sonochemical installations, which contributes to the separation of a large number of conglomerates. The effect of aeration on the flotation process of nanoscale particles is described. Conducting experiments on laboratory experimental flotation machine in different modes and with different flotation reagents. A method of conditioning the pulp, which increases the efficiency of flotation and, as a consequence, the quality of the output products. The dependences of the foam layer height on the concentration of the foaming agent, the dependence of the quality and quantity of the output products on the time and flotation regime are constructed. Important conditions for providing a high degree of separation of micro-sized media are determined. This solution was developed for the enrichment of the cyclone dust gas purification silicon. The study identified the main features of the flotation separation of silicate and carbon phases of cyclone dust. The technical solutions allowing to make effective separation despite the revealed features are offered. Application of this technology leads to reduction of sludge accumulation near silicon plants and production of innovative modifiers for various industries.

Toxicity to bronchial cells and endocrine disruptive potentials of indoor air and dust extracts and their association with multiple chemical classes

Pollution of indoor environment, where people spend much of their time, comprises complex mixtures of compounds with vastly understudied hazard potential. This study examined several important specific toxic effects and pollutant levels (177 compounds) of indoor samples (air gas phase, PM10 and dust) from different microenvironments after two extractions with focus on their gas/particle/dust distribution and polarity. The endocrine disruptive (ED) potential was assessed by human cell-based in vitro bioassays addressing anti-/estrogenicity, anti-/androgenicity, aryl hydrocarbon, thyroid and peroxisome proliferator-activated receptor-mediated activities. Potential toxicity to respiratory tract tissue was assessed using human bronchial cell line. The toxicological analyses pointed out the relevance of both inhalation and ingestion exposure, with significant effects detected after exposure to extracts from all three studied matrices with distinct gas/particle distribution patterns. Chemical analyses document the high complexity of indoor pollutant mixtures with greatest levels of phthalates, their emerging alternatives, and PAHs in dust. Despite the detection of up to 108 chemicals, effects were explained only to low extent. This emphasizes data gaps regarding ED potencies of many detected abundant indoor contaminants, but also potential presence of other unidentified ED compounds. The omnipresent ED potentials in indoor environment rise concern regarding associated human health risk.

Performance of reduction on particle emission by combining the charged water drop atomization and electric field in wet electrostatic precipitator

In this study, a wet electrostatic precipitator (WESP) with combination of electric field and charged water drop atomization was designed for fine particle collection, which replaced the traditional water film and mechanically spray. The removal performance was evaluated considering applied voltage, water flow rate, gas residence time, dust concentration, and continuous operation time. Results indicated that supplying charged droplets could acquire higher discharge current and better agglomeration effect than the dry type. The maximum penetration ratio was reduced from 3.8%−11.56% in the dry ESP to 3.58%−8.6% with charged droplets, as the applied voltage increased from 30 kV to 60 kV. Meanwhile, increase of water flow rate improved the total removal efficiency. The advantage of the WESP was more obvious under short gas residence time. The route of synergistically increasing gas residence time and applied voltage could largely reduce the penetration ratio, which decreased from 6.99%−19.81% to 1.03%−2.43% as they were enhanced from 1.50 s and 30 kV to 3.33 s and 60 kV. Increasing the dust concentration led to the trend that the total removal efficiency first increasing and then decreasing gradually, resulted from combined mechanisms of particle agglomeration and suppression of corona current. Moreover, the atomization of charged water drop maintained the advantage on particle removal under continuous operation, and the efficiency drop after long-term operation could be avoided. In particular, the WESP achieved significant reduction on water consumption compared to conventional large-scale and on-site WESPs in application with equivalent levels of removal efficiency.

C&EN talks with Karin Öberg, astrochemist

The universe is 13.8 billion years old—and like many things that have been around for a while, it’s collected lots of dust. And just one of these dust particles could seed an entire planet. After a star is born, it becomes surrounded by a rotating disk of gas and silicate dust particles. Here, in the nursery of a new solar system, the temperature is just a few degrees above absolute zero. The surfaces of the swirling dust grains become coated with ice and serve as miniature laboratories in which the chemical building blocks of nascent planets are concocted. Over millions of years, the dust grains collide and stick together, creating larger and larger bodies and eventually growing into planets. Astrochemists like Karin Öberg aim to understand how those infinitesimal icy grains seed solar systems beyond our own—and perhaps contribute to life on other worlds. Her lab at Harvard University combines

Application of coal seam grouting to prevent and extinguish fire technology in Fusheng Coal Mine

Spontaneous combustion of coal not only releases toxic and harmful gases, but also may cause gas and coal dust explosions to endanger the lives of miners. The No.15 coal seam of Fusheng Coal Mine in Shanxi has a short period of spontaneous combustion and is prone to spontaneous combustion. In order to prevent spontaneous combustion of coal seams, it is proposed to use grouting to prevent fire extinguishing technology, mainly through the design of grouting system, the selection of grouting materials, the calculation of grouting parameters, the optimization of grouting technology and the selection of grouting equipment, etc. And it establishes methods for monitoring the effects of grouting zone temperature and gas composition, fire-fighting grouting accounts, etc. A series of grouting safety technical supporting measures such as grouting work system, prevention of pipe blockage, prevention of slurry running, setting of filter slurry sealing and drainage channels, etc. are proposed.

Modern methods for purification of emissions from ferrous metallurgy enterprises

The article systematizes the characteristics of emissions of toxic substances from the main processing in ferrous metallurgy: dust, organic and inorganic gas toxins. It is shown that methods for capturing emissions from metallurgical dust are still based on the use of inertial and electrostatic forces and a filtration method. The greatest cleaning effect is provided by cloth filters and electrostatic precipitators. Currently, there are filter materials for high-temperature gas purification (up to 1000˚C), and electrostatic precipitators that allow capturing highly dispersed particles. Improvement of wet apparatuses is moving towards the creation of high-pressure scrubbers and centrifugal apparatus that provide cooling and purification of gases from submicron dust and gaseous toxins. It is shown that at present there are various methods of gas purification from organic and inorganic toxins based on the phenomena of sorption, oxidation and reduction in the presence of catalysts and without them, as well as under electronic, light and radiation exposure. When choosing devices for cleaning metallurgical emissions, preference should be given to those in which the processes of capturing dust and toxic gases are combined.

Investigating Cold Dust Properties of 12 Nearby Dwarf Irregular Galaxies by Hierarchical Bayesian Spectral Energy Distribution Fitting

Abstract Combining infrared and submillimeter observations and applying a two-temperature modified blackbody (TMBB) model with a hierarchical Bayesian technique, we model the spectral energy distribution of 12 nearby dwarf irregular (dIrr) galaxies. We aim to probe potential submillimeter excess emission at 350, 500, and 850 μm and investigate the properties of cold dust parameters. Based on the TMBB model with cold dust emissivity index (β c) fixed to 2, one galaxy shows 500 μm excess emission and nine galaxies show excess at 850 μm (five of them still show 850 μm excess in the case of free β c). We find that the 850 μm excess emission is easily detected in the dIrr galaxies with low star formation activity. The 850 μm excess is more frequent and more prominent in dIrr galaxies with low molecular hydrogen gas mass fraction or low ratios between cold dust mass and gas mass. As galaxies evolve, the ratios between atomic hydrogen gas mass and stellar mass decrease and the 850 μm excess emission tends to decrease or even disappear. Our results suggest that the cold dust temperature may increase, as the dIrr galaxies have more intense star formation or richer metallicity. There is a weak anticorrelation between the cold dust-to-stellar mass ratio and the specific star formation rate for our galaxies.

Remarkably high mass and velocity dispersion of molecular gas associated with a regular, absorption-selected type I quasar

We present 3 mm observations of the quasar J0015+1842 at z = 2.63 with the NOrthern Extended Millimeter Array (NOEMA). Our data reveal molecular gas, traced with a Gaussian CO(3–2) line, with a remarkably high velocity dispersion (FWHM = 1010 ± 120 km s−1) that corresponds to a total molecular mass MH2 ≈ (3.4 − 17) × 1010 M⊙, depending on the adopted CO-to-H2 conversion factor αCO = (0.8 − 4.0) M⊙ (km s−1 pc2)−1. Assuming the 3 mm continuum emission is thermal, we derive a dust mass of about Mdust ∼ 5 × 108 M⊙. J0015+1842 is located in the molecular gas-rich region in the IR versus CO line luminosity diagram, in between the main locus of main-sequence and sub-millimetre galaxies and that of most other active galactic nuclei targeted so far for CO measurements. While the high velocity dispersion of the CO line suggests a merging system, J0015+1842 is observed to be a regular, only very moderately dust-reddened (AV ∼ 0.3 − 0.4) type I quasar from its UV-optical spectrum, from which we infer a mass of the super-massive black hole of about MBH ≈ 6 × 108 M⊙. We suggest that J0015+1842 is observed at a galaxy evolutionary stage where a massive merger has brought significant amounts of gas towards an actively accreting super-massive black hole (quasar). While the host still contains a large amount of dust and molecular gas with a high velocity dispersion, the quasar has already cleared the way towards the observer, likely through powerful outflows, as has recently been revealed by optical observations of the same object. High angular resolution observations of this and similar systems are expected to help us better determine the respective importance of evolution and orientation in the appearance of quasars and their host galaxies. These observations have the potential to investigate early feedback and star-formation processes in galaxies in their quasar phases.

The dust-gas AGN torus as constrained from X-ray and mid-infrared observations

Context. In recent decades, several multiwavelength studies have been dedicated to exploring the properties of the obscuring material in active galactic nuclei (AGN). Various models have been developed to describe the structure and distribution of this material and constrain its physical and geometrical parameters through spectral fitting techniques. However, questions around the way in which torus mid-infrared (mid-IR) and X-ray emission are related remain unanswered. Aims. In this work, we aim to study whether the dust continuum at mid-IR and gas reflection at X-rays have the same distribution in a sample of AGN. Methods. We carefully selected a sample of 36 nearby AGN with NuSTAR and Spitzer spectra available that satisfy the following criteria: (1) the AGN component dominates the mid-IR spectra (i.e., the stellar and interstellar medium components contribute less than 50% to the spectrum), and (2) the reflection component contributes significantly to the X-ray spectrum. Furthermore, we discarded the sources whose reflection component could be produced by ionized material in the disk. We derived the properties of the nuclear dust and gas through a spectral fitting, using models developed for mid-IR and X-ray wavelengths assuming smooth and clumpy distributions for this structure. Results. We find that a combination of smooth and clumpy distributions of gas and dust, respectively, is preferred for ∼80% of sources with good spectral fits according to the Akaike criterion. However, considering extra information about each individual source, such as the absorption variability, we find that ∼50% of our sources are best described by a clumpy distribution of both dust and gas. The remaining ∼50% of our sources can still be explained with a smooth distribution of gas and a clumpy distribution of dust. Furthermore, we explored the torus dust-to-gas ratio, finding that it is [0.01–1] times that of the interstellar medium. Conclusions. The results presented in this paper suggest that the distribution of the gas and dust in AGN is complex. We find at least six scenarios to explain the observed properties of our sample. In these scenarios, three gas–dust distribution combinations are possible: clumpy–clumpy, smooth–smooth, and smooth–clumpy. Most of them are in agreement with the notion that gas could also be located in the dust-free region, which is consistent with the dust-to-gas ratio found.

Analysis of Hybrid Gas–Dust Outbursts Observed at 67P/Churyumov–Gerasimenko

Abstract Cometary outbursts offer a valuable window into the composition of comet nuclei with their forceful ejection of dust and volatiles in explosive events, revealing the interior components of the comet. Understanding how different types of outbursts influence the dust properties and volatile abundances, to better interpret what signatures can be attributed to primordial composition and what features are the result of processing, is an important task best undertaken with a multi-instrument approach. The European Space Agency Rosetta mission to 67P/Churyumov–Gerasimenko carried a suite of instruments capable of carrying out this task in the near-nucleus coma with unprecedented spatial and spectral resolution. In this work, we discuss two outbursts that occurred 2015 November 7 and were observed by three instruments on board: the Alice ultraviolet spectrograph, the Visual Infrared and Thermal Imaging Spectrometer, and the Optical, Spectroscopic, and Infrared Remote Imaging System. Together, the observations show that mixed gas and dust outbursts can have different spectral signatures representative of their initiating mechanisms, with the first outburst showing indicators of a cliff collapse origin and the second more representative of fresh volatiles being exposed via a deepening fracture. This analysis opens up the possibility of remote spectral classification of cometary outbursts with future work.

Investigating the Relative Gas and Small Dust Grain Surface Heights in Protoplanetary Disks

Abstract Dust evolution in protoplanetary disks from small dust grains to pebbles is key to the planet formation process. The gas in protoplanetary disks should influence the vertical distribution of small dust grains (∼1 μm) in the disk. Utilizing archival near-infrared polarized light and millimeter observations, we can measure the scale height and flare parameter β of the small dust grain scattering surface and 12CO gas emission surface for three protoplanetary disks: IM Lup, HD 163296, and HD 97048 (CU Cha). For two systems, IM Lup and HD 163296, the 12CO gas and small dust grains at small radii from the star have similar heights, but at larger radii (>100 au), the dust grain scattering surface height is lower than the 12CO gas emission surface height. In the case of HD 97048, the small dust grain scattering surface has similar heights to the 12CO gas emission surface at all radii. We ran a protoplanetary disk radiative transfer model of a generic protoplanetary disk with TORUS and showed that there is no difference between the observed scattering surface and 12CO emission surface. We also performed analytical modeling of the system and found that gas-to-dust ratios larger than 100 could explain the observed difference in IM Lup and HD 163296. This is the first direct comparison of observations of gas and small dust grain height distribution in protoplanetary disks. Future observations of gas emission and near-infrared scattered-light instruments are needed to look for similar trends in other protoplanetary disks.

Research on the integration of flue gas desulfurization and dust removal in oil shale refining

The flue gas of oil shale retort is characterized by high humidity, low sulfur content and tar content, which makes it impossible for traditional flue gas desulfurization facilities to deal with such flue gas normally. By collecting flue gas parameters at the inlet and outlet of the original desulfurization tower of oil shale dry distillation flue gas, and combining with computational fluid dynamics numerical simulation, this paper analyzes the fault reasons of each step in the process of desulfurization of oil shale dry distillation flue gas. Through experimental study, the flocculation characteristics of suspended solids and petroleum substances in desulfurization circulating liquid were analyzed. The results show that the low concentration of Na2CO3, Ca(HO)2, CaO desulfurizer can promote the flocculation, Ca(HO)2, CaO desulfurizer is beneficial to the removal of petroleum substances. The original wet limestone-gypsum desulfurization system was transformed into the wet sodium carbonate desulfurization and dust removal integrated system. The method of flocculation and sedimentation is used to remove sludge and petroleum substances, which can ensure the normal operation of the system and the emission of flue gas up to the standard.

Production of modifying additives for highways

The article presents a description and operating parameters of the technological process for the production of modifying additives for concrete and asphalt concrete based on exhaust gas dust in the production of silicon by operations. Described is a foam product, which is a raw material for obtaining fullerene-like carbon, a modifying additive MD2, and a chamber product for spherical silicon dioxide, a modifying additive MD1. The regulated parameters have been worked out, the regulation limits and the norms of expenses are given. The development of a functional diagram is based on the analysis of the technological process, as an object of automation, in which the main control and controlled influences are distinguished, which must be regulated and maintained within specified limits, in order to obtain the final product with the required quality characteristics. The implementation of this scheme is presented in this work. It combines a flow diagram and technical means measuring, controlling and regulating these flows, in order to ultimately obtain products of the desired quality.

Conditions for Justifying Single-fluid Approximation for Charged and Neutral Dust Fluids and a Smoothed Particle Magnetohydrodynamics Method for Dust–Gas Mixture

Abstract We describe a numerical scheme for magnetohydrodynamics simulations of dust–gas mixture by extending smoothed particle magnetohydrodynamics. We employ the single-species particle approach to describe dust–gas mixture with several modifications from the previous studies. We assume that the charged and neutral dust can be treated as single-fluid, that the electromagnetic force acts on the gas, and that that acting on the charged dust is negligible. The validity of these assumptions in the context of protostar formation is not obvious and is extensively evaluated. By investigating the electromagnetic force and electric current with terminal velocity approximation, it is found that as the dust size increases, the contribution of dust to them becomes smaller and negligible. We conclude that our assumption that the electromagnetic force on the dusts is negligible is valid for the dust size with a d ≳ 10 μm. On the other hand, they do not produce the numerical artifact for the dust a d ≲ 10 μm in the envelope and disk, where the perfect coupling between gas and dust is realized. However, we also found that our assumptions may break down in outflow (or under an environment with very strong magnetic field and low density) for the dust a d ≲ 10 μm. We conclude that our assumptions are valid in almost all cases where macroscopic dust dynamics is important in the context of protostar formation. We conduct numerical tests of dusty waves, dusty magnetohydrodynamics shocks, and gravitational collapse of magnetized cloud cores with our simulation code. The results show that our numerical scheme well reproduces the dust dynamics in the magnetized medium.

Job Safety Analysis during Tunnel Construction

Purpose: There are many tunnels under construction in Nepal as its mountainous country. Road, water supply, hydropower, and irrigation projects are under construction in Nepal through the tunnel. “Safety First” should be one of the main objectives of any construction projects mainly tunnel and shall be given high priority throughout the construction period. A single person alone cannot do it alone. A team including safety professionals to concentrate on health, safety, and environmental concerns shall be involved to ensure that safety environment will be maintained in the construction site. OSH is the relation between man and man, man and machine and man and environment. The paper aims to analyze the job safety of major selected construction activities during tunneling. Design/Methodology/Approach: Site Observation, Key Informant Interview (KII), and Study of Methods of Statement were done as main data collection tools. Job safety analysis and identification of activity with high risk level involved should be determined so that proper prevention and control mechanism could be determined and implemented. Drilling, excavation, blasting, mocking, scaling and shotcerting were major activities whose hazards, prevention mechanism and the responsible party were identified. Findings/Result: The study reveals that the main occupational hazards were mechanical and chemical hazards. Rockfall and landslide were noted as the major mechanical hazard whereas toxic gas and cement dust were the main chemical hazards. Similarly, noise and vibration were the main physical hazards and untimely payment of wages and leave were psychological hazards. It was reported that the major accident occurred at sites where the leg struck on steps of boomer while pulling a worker to save him from falling of boomer, penetration by fine grinding wheel material into the eye while carrying out grind cutting of drum and faint due to oxygen deficiency inside the tunnel. Some minor accidents were road traffic accidents, cut by sharp tools, fall/hit to/hit by objects, splashing of acids, burning caught by fire, etc. and the fatal accidents was one of the mechanics blown away by the erupted boomer tyres while filling up air into the same and one of the workers lost his life due to truck accident inside the work premise. The families of the demised had been compensated by the company. For safe construction requires the teamwork of sincere and coordinated effort of all stakeholders. Lack of regular inspection and monitoring at the site was the main cause of improper implementation of prevailing health and safety regulations. Originality/Value: The study is highly significant for working engineers to perform the task without any misfortune inside the tunnel. Paper Type: Project Management Action Research.