Cassette Filter Research Articles

Exposures to Polycyclic Aromatic Hydrocarbons and Their Mitigation in Wildland Firefighters in Two Canadian Provinces.

We aimed to characterize polycyclic aromatic hydrocarbons (PAHs) in the breathing zone and on the skin of wildland firefighters and to assess their contribution to urinary 1-hydroxypyrene (1-HP) over repeated firefighting rotations. We asked if improved skin hygiene or discretionary use of an N95 mask would reduce absorption. In collaboration with wildfire services of two Canadian provinces, Alberta and British Columbia (BC), we recruited wildland firefighters from crews willing to be followed up over successive rotations and to be randomly assigned to normal practice, enhanced skin hygiene (ESH), or ESH plus discretionary use of an N95 mask. We collected spot urine samples at the beginning and end of up to four rotations/firefighter. On designated fire days, as close as possible to the end of rotation, we collected skin wipes from the hands, throat, and chest at the beginning and end of the fire day and, in BC, start of fire-day urine samples. Volunteers carried air monitoring pumps. Participants completed questionnaires at the beginning and end of rotations. Exposure since the start of the fire season was estimated from fire service records. Urinary 1-HP was analyzed by LC-MS-MS. Analysis of 21 PAHs on skin wipes and 27 PAHs from air sampling was done by GC-MS-MS. Statistical analysis used a linear mixed effects model. Firefighters in Alberta were recruited from five helitack crews and two unit crews, and in BC from two unit crews with 80 firefighters providing data overall. The fire season in BC was very active with five monitored fire days. In Alberta, with more crews, there were only seven fire days. Overall, log 1-HP/creatinine (ng/g) increased significantly from the start (N = 145) to end of rotation (N = 136). Only three PAHs (naphthalene, phenanthrene, and pyrene) were found on >20% of skin wipes. PAHs from 40 air monitoring pumps included 10 PAHs detected on cassette filters (particles) and 5 on sorbent tubes (vapor phase). A principal component extracted from air monitoring data represented respiratory exposure and total PAH from skin wipes summarized skin exposure. Both routes contributed to the end of rotation urinary 1-HP. The ESH intervention was not demonstrated to effect absorption. Allocation of an N95 mask was associated with lower 1-HP when modeling respiratory exposure (β = -0.62, 95% CI -1.15 to -0.10: P = 0.021). End of rotation 1-HP was related to 1-HP at the start of the next rotation (β = 0.25, 95% CI 0.12 to 0.39: P < 0.001). Exposures to PAHs during firefighting were significant, with samples exceeding the American Conference of Governmental Industrial Hygienists Biological Exposure Index for 1-HP suggesting a need for control of exposure. PAH exposure accumulated during the rotation and was not fully eliminated during the break between rotations. Both respiratory and skin exposures contributed to 1-HP. While improved skin hygiene may potentially reduce dermal absorption, that was not demonstrated here. In contrast, those allocated to discretionary use of an N95 mask had reduced 1-HP excretion. Wildland firefighters in North America do not use respiratory protection, but the results of this study support more effective interventions to reduce respiratory exposure.

Exposure to bacterial and fungal bioaerosols in facilities processing biodegradable waste.

The aim of the study was to determine the exposure of workers within biodegradable waste processing facilities to bacteria and fungi to identify any exposures of potential concern to health. Occupational measurements were performed in six composting and three bioenergy (bioethanol or methane/biogas) producing facilities. Bioaerosols were measured from breathing zones with Button aerosol or open face cassette filter samplers, and swab specimens were taken from the nasal mucous membranes of the workers. Aspergillus fumigatus, Bacillus cereus group, Campylobacter spp., Salmonella spp., Streptomyces spp., and Yersinia spp. were determined by real-time polymerase chain reaction (qPCR). A. fumigatus, and mesophilic and thermophilic actinobacteria were also cultivated from filters. Bacterial airborne endotoxins collected by IOM samplers were analyzed using a Limulus assay. Bioaerosol levels were high, especially in composting compared to bioenergy producing facilities. Endotoxin concentrations in composting often exceeded the occupational exposure value of 90 EU/m3, which may be harmful to the health. In addition to endotoxins, the concentrations of A. fumigatus (up to 2.4 × 105 copies/m3) and actinobacteria/Streptomyces spp. (up to 1.6 × 106 copies/m3) in the air of composting facilities were often high. Microbial and endotoxin concentrations were typically highest in waste reception and pre-treatment, equal or decreased during processing and handling of treated waste, and lowest in wheel loader cabins and control rooms/outdoors. Still, the parameters measured in wheel loader cabins were often higher than in the control sites, which suggests that the use of preventive measures could be improved. B. cereus group, Salmonella spp., and Yersinia spp. were rarely detected in bioaerosols or nasal swabs. Although Campylobacter spp. DNA was rarely detected in air, as a new finding, Campylobacter ureolyticus DNA was frequently detected in the nasal mucous membranes of workers, based on partial 16S rDNA sequencing. Moreover, especially A. fumigatus and C. ureolyticus spp. DNA concentrations in swabs after the work shift were significantly higher than before the shift, which indicates their inhalation or growth during the work shift. Microbial qPCR analysis of bioaerosols and swab samples of nasal mucosa allowed measuring exposure in various work operations and during the work shift, identifying problems for health risk assessment to improve working conditions, and evaluating the effectiveness of preventive measures and personal protection of workers.

Toxicologic Testing of Wastewater in Vladivostok on Marine Microalgae Heterosigma Akashiwo

Studies were performed to determine a toxicity of wastewater before being fed to disposal facility, after biological and various methods of water treatment. The marine microalgae Heterosigma akashiwo isolated in Peter the Great Bay (Sea of Japan, Vladivostok) was used as a test object. Comparative analysis outcomes presentation regarding wastewater samples before being supplied to disposal facilities, wastewater samples after secondary sedimentation tanks, a self-cleaning sand filter, a semi-industrial installation – a slow cassette filter, and polished effluents by chemicals.

Improving the Effectiveness of Filter Regeneration by Pulse Scavenging

Scientific research and experimental-design work are performed to improve the effectiveness of regenerating bag and cassette filters by reverse pulse scavenging. It is recommended that the velocity and flow rate of the compressed air used for scavenging be chosen as the regime parameters, depending on the physico-mechanical properties of the dust that is being captured. A method of calculating the grouped distribution of collectors is proposed to uniformly distribute the compressed air among the scavenging nozzles. It is also recommended that swirl nozzles be used to equalize the pressure pulses along the filter elements.

A Comparison of the Closed-Face Cassette at Different Orientations While Measuring Total Particles

The current method for sampling aerosols using the 37-mm closed-face cassette (CFC) sampler is based on the orientation of the cassette at ∼45° from horizontal. There is some concern as to whether this method is appropriate and may be underestimating exposures. An alternative orientation at ∼0° (horizontal) has been discussed. This research compared the CFC's orientation at 45° from horizontal to the proposed orientation at horizontal, 0° in a controlled laboratory setting. The particles used in this study were fused alumina oxide in four sizes, approximately 9.5 μm, 12.8 μm, 18 μm, and 44.3 μm in aerodynamic diameter. For each test, one aerosol was dispersed in a wind tunnel operating at 0.2 m/s with samplers mounted in the breathing zone of a rotating mannequin. A sampling event consisted of four pairs of samplers, placed side by side (one pair at 45° and another at 0° cassette orientation), and exposed for a period of 45 minutes. A total of 12 sampling events, 3 sample events per particle size, were conducted with a total of 94 samples collected. Mass concentration measurements were compared to assess the relationship between the sampler orientations of the cassettes. In addition, the relationship between the mass collected on the cassette filter and on the interior walls of the cassette was also assessed. The results indicated that there was no significant difference between the measured concentrations based on the orientation of the CFCs. The amount of mass collected on the interior walls of the cassettes was relatively low (<5%) compared to expected (up to 100%) wall losses for both orientations.

Evaluation of sampling methods for Bacillus spore-contaminated HVAC filters

The objective of this study was to compare an extraction-based sampling method to two vacuum-based sampling methods (vacuum sock and 37mm cassette filter) with regards to their ability to recover Bacillus atrophaeus spores (surrogate for Bacillus anthracis) from pleated heating, ventilation, and air conditioning (HVAC) filters that are typically found in commercial and residential buildings. Electrostatic and mechanical HVAC filters were tested, both without and after loading with dust to 50% of their total holding capacity. The results were analyzed by one-way ANOVA across material types, presence or absence of dust, and sampling device. The extraction method gave higher relative recoveries than the two vacuum methods evaluated (p≤0.001). On average, recoveries obtained by the vacuum methods were about 30% of those achieved by the extraction method. Relative recoveries between the two vacuum methods were not significantly different (p>0.05). Although extraction methods yielded higher recoveries than vacuum methods, either HVAC filter sampling approach may provide a rapid and inexpensive mechanism for understanding the extent of contamination following a wide-area biological release incident.

LARGE EDDY SIMULATION FOR UNSTEADY TURBULENT FLOW IN THIN SLAB CONTINUOUS CASTING MOLD

The unsteady turbulent flow during the continuous casting of steel is important, because it influences critical phenomena that affect steel quality. Unsteady three-dimensional flow in the mold region of the liquid pool during continuous casting of steel slabs has been computed using realistic geometries starting from the submerged inlet nozzle to the mold. The cassette filter function was used to deal with unsteady Navier-Stokes equation, and then the turbulent flow in the thin slab CCM was simulated with the large eddy simulation method combined with the Smagorinsky sub-grid scale model in this paper. And the model was verified by the Particle Image Velocimetry (PIV) experimental results which was got from a relate scientific literature. In this thesis, by means of LES, the flow characteristics in the thin slab CCM were acquired, such as the vortex distribution, the formation of the large eddy coherent structures, development, shedding and fracture process. In the same time, the turbulent asymmetric distribution was revealed even the nozzle in the centre position. Interactions between the two halves cause large velocity fluctuations near the meniscus. And the vortex is located at the low velocity side adjacent to the SEN. Along with the unsteady time development, the unsteady turbulent large vortex structures of the liquid steel in the CCM presented periodic bias flow distribution, and the period is about 20 seconds.

Turbulent Flow of Molten Steel in Thin Slab Continuous Casting Mold

The quality of continuously casting steel is greatly influenced by turbulent flow in the mold. Understanding the unsteady flow structures in this process is an important step in avoiding failures and decreasing defects. The cassette filter function is used to deal with unsteady Navier-Stokes equation, and then the turbulent flows in the thin slab continuous casting processes are simulated with the large eddy simulation (LES) method with the Smagorinsky sub-grid scale model. Characteristics of the unsteady turbulent flow in the thin slab continuous casting processes are exhibited. The turbulent asymmetric distribution was revealed even the nozzle in the centre position. And the vortices are located at the low velocity side adjacent to the nozzle.

Sampling Results of the Improved SKC Diesel Particulate Matter Cassette

Diesel particulate matter (DPM) samples from underground metal/nonmetal mines are collected on quartz fiber filters and measured for carbon content using National Institute of Occupational Safety and Health Method 5040. If size-selective samplers are not used to collect DPM in the presence of carbonaceous ore dust, both the ore dust and DPM will collect on the quartz filters, causing the carbon attributed to DPM to be artificially high. Because the DPM particle size is much smaller than that of mechanically generated mine dust aerosols, it can be separated from the larger mine dust aerosol by a single-stage impactor. The SKC DPM cassette is a single-stage impactor designed to collect only DPM aerosols in the presence of carbonaceous mine ore aerosols, which are commonly found in underground nonmetal mines. However, there is limited data on how efficiently the SKC DPM cassette can collect DPM in the presence of ore dust. In this study we investigated the ability of the SKC DPM cassette to collect DPM while segregating ore dust from the sample. We found that the SKC DPM cassette accurately collected DPM. In the presence of carbon-based ore aerosols having an average concentration of 8 mg/m 3 , no ore dust was detected on SKC DPM cassette filters. We did discover a problem: the surface areas of the DPM deposits on SKC DPM cassettes, manufactured prior to August 2002, were inconsistent. To correct this problem, SKC modified the cassette. The new cassette produced, with 99% confidence, a range of DPM deposit areas between 8.05 and 8.28 cm 2 , a difference of less than 3%.

The influence of pleat geometry on the pressure drop in deep-pleated cassette filters

In air filtering applications, a filter's pressure drop at a defined collection efficiency constitutes an important parameter. This paper discusses the variables influencing the pressure drop in air filters featuring deep-pleated filter media. For cassette-type fine filters in accordance with EN 779 or for HEPA/ULPA filters in accordance with EN 1822, the most commonly used media are paper-like materials with a thickness of less than 1 mm, which offer a relatively high resistance to the air flowing through them. Manufacturers accordingly endeavour to accommodate a maximum of filter medium area in a small space. To enable the pressure drops customary in intake, exhaust and re-circulated air filtration to be assured, the filter medium is therefore arranged in narrow, deep pleats. Particularly when large quantities of air are being handled per filter element, it is advantageous to pleat the filter medium in depths of 150 mm to 280 mm. The conversion technique and the resultant pleat geometry exert a crucial influence on the pressure drop concerned.

Particle precharging and fabric filtration - experimental results of a corona precharger

A corona precharger has been installed in front of a pilot-sized, pulse jet cassette filter. Experiments under ambient conditions with re-dispersed fly ash as well as experiments at higher gas temperatures (up to 130°C) have been performed. The net electrostatic charge on the particles was measured directly behind the precharger. The effect of the corona pre-charge, the triboelectric charge and discharging the particles on the filtration behaviour of the fly ashes was evaluated. The pressure loss of the dust cake as well as the cycle time between back-pulse cleaning was improved under certain conditions. Collection efficiency has been enhanced by charging of the fly ash particles. It has been observed that the beneficial effect of the particle precharging depends strongly on the gas velocity in the system, the dust concentration and the tribocharge on the fly ash. Back-corona effects in the precharger unit had been detected. It was tried to suppress these negative effects on performance by intermittent energization of the high-voltage power supply connected to the corona precharger. The results of these experiments will be presented and discussed.

Determination of Cyanuric Acid or Trichloroisocyanuric Acid in Air

Abstract An analytical procedure for measurement of cyanuric acid or trichlor oisocyanuric acid in air has been developed. The procedure involves air sampling with a 37-mm PVC membrane filter, recovery with a phosphate buffer, and analysis by high performance liquid chromatography with a UV detector at 225 nm. The interior surface of the front piece of the cassette filter holder also is analyzed. Average recoveries were 0.98 to 1.00 after fortification of PVC filters with 12- to 412-μg quantities of cyanuric acid. Average recoveries of trichloroisocyanuric acid were 0.83 to 0.98 after fortification of glass surfaces with 12- to 424-μg quantities (these are reasonable approximations for recoveries of trichloroisocyanuric acid from PVC filters). The analyst should ascertain which analyte is present at the sampling site because trichloroisocyanuric acid reacts with water in the phosphate buffer to form cyanuric acid in high yield.

Asbestos Fiber Deposition Patterns on Various 25-mm Cassette Filters at a High Flow Rate

Abstract Although the membrane filter sampling methods for airborne asbestos fibers employing either phase contrast microscopy or electron microscopy produce very highly variable results, they frequently are used to make critical decisions on the need for further decontamination. Radial differences in density of fiber deposition on the filter surface, reported to occur at lower flow rates, could produce biased measurements if counting fields are not representative of the airborne fiber levels and could contribute to intercounter variability if field selection protocols are not consistent. Here the uniformity of deposition was evaluated for nine commercial cassette filter configurations (seven with 50-mm conductive cowls, one with a cowl and a bell-shaped inlet attachment, and one with a bell-shaped inlet but without a cowl). A fluidized bed aerosol generator produced a test atmosphere containing chrysotile asbestos fibers. Moist air (30 percent relative humidity), electrical grounding, and an aerosol neut...

Characterization of dusts collected from swine confinement buildings.

As part of a project to evaluate health hazards for workers in swine confinement buildings, the air in 21 different buildings was sampled with 37 mm cassette filters with and without cyclone preselectors and with cascade impactors. Filter results yielded a mean total aerosol of 6.3 mg/m3, a mean respirable aerosol of 0.5 mg/m3; the geometric mean diameter was 2.9 microns. Cascade impactor measurements revealed a mean total aerosol of 7.6 mg/m3, a respirable aerosol of 2.5 mg/m3 and a mass median diameter of 9.6 microns. The two major constituents in these aerosols were grain particles and dried fecal matter. The grain particles were larger than fecal particles and proportionately more abundant in finishing buildings where 50 kg X 100 kg animals are housed. Therefore the respirable fraction was less in finishing buildings than in farrowing and nursery buildings. Culturing of settled dusts yielded six different mold species, with the highest counts for Verticillium sp. (5 X 10(2) cfu/mg dry dust) grown at 37 degrees C. Thermophilic Actinomycetes and both gram negative and gram positive bacteria were isolated. Azocasein proteinase activity was found in most dust samples analyzed. This dust had a protein content of about 23% and a mean adsorbed ammonia content of 0.4%.

Characterization of Dusts Collected from Swine Confinement Buildings

As part of a project to evaluate health hazards for workers in swine confinement buildings, the air in 21 different buildings was sampled with 37 mm cassette filters with and without cyclone preselectors and with cascade impactors. Filter results yielded a mean total aerosol of 6.3 mg/m3, a mean respirable aerosol of 0.5 mg/m3; the geometric mean diameter was 2.9 microns. Cascade impactor measurements revealed a mean total aerosol of 7.6 mg/ m3, a respirable aerosol of 2.5 mg/ m3 and a mass median diameter of 9.6 microns. The two major constituents in these aerosols were grain particles and dried fecal matter. The grain particles were larger than fecal particles and proportionately more abundant in finishing buildings where 50 kg-100 kg animals are housed. Therefore the respirable fraction was less in finishing buildings than in farrowing and nursery buildings. Culturing of settled dusts yielded six different mold species, with the highest counts for Verticillium sp. (5 × 102 cfu/mg dry dust) grown at 37° C. Thermophilic Actinomycetes and both gram negative and gram positive bacteria were isolated. Azocasein proteinase activity was found in most dust samples analyzed. This dust had a protein content of about 23% and a mean adsorbed ammonia content of 0.4%.

CAMPEDS--a dust sampling and assessment system for use in hard rock mines.

A dust sampling system comprising gravimetric assessment by weighing and quartz assessment by X-ray diffraction, as developed by the Elliot Lake Laboratory for use in hard rock mines, is described. The compromises made between the sometimes conflicting requirements of sampling, ashing, weighing, quartz assessment and pump performance are stressed. Emphasis is given to the need for defining the total dust sampling and analysis system, including the calibration procedures. The system incorporates: (1) a small impactor size selector and integral cassette filter holder, mounted with the pump on the miner's cap lamp battery; (2) a silver membrane filter 25 mm in diameter; (3) gravimetric assessment before and after ashing; (4) X-ray diffraction assessment for quartz; (5) computer controlled diffractometer. Alternatives are available for lapel sampling or, using a pump driven by a light-weight battery, fixed station sampling or personal sampling on surface. Size-selection is calibrated, by comparison with a reference sampler, while quartz calibration is by collection of samples in a pure quartz airborne dust cloud. The advantages of the system are: rapid assessment of quartz, with low requirements for technician time and skill; high throughput capacity—10 000 samples per year per X-ray diffractometer; easy logistics for personal sampling in underground mines; robust sampler and samples; high resistance to contamination of respirable dust by coarse dust.

Effects of electrostatic charge on aerosol collection with polystyrene filter cassettes.

Electrostatic fields are present on polystyrene cassette filter holders commonly used to measure the concentration of particles in air. Beryllium concentrations were determined at a beryllium refinery using neutral, and positively and negatively charged cassettes. In laboratory experiments, tobacco smoke, magnetite and polyvinyltoluene latex spheres were collected by both charged and neutral cassettes. No differences in concentration measurements were observed in the experiments at the refinery. In the laboratory experiments, the concentration of a charged negative aerosol collected by a highly charged negative cassette was reduced. Thus, when collecting charged aerosols, the polystyrene cassettes should be charge neutralized.