Feet Of Air Research Articles

Visible dust and asbestos: what does it suggest regarding asbestos exposures?

Courts in asbestos litigation in the past decade have increasingly required quantitation of asbestos exposures beyond arguments that the exposures exceeded de minimis or background levels. Exposure levels for those in the past were often either not measured or minimally measured. Similar Exposure Groups (SEGs) methods can be considered, however i) the available data to be used for comparison may not well reflect the exposures of the individual of interest and ii) past data/standards were taken in units of million particles per cubic foot of air (mppcf) as opposed to fibers per cubic centimeter (f/cc).1 The purpose of this work was to research these two issues to determine if exposure to visible dust created from asbestos-containing materials (ACM) (>1% asbestos) likely exceeds recommended asbestos exposure limits. This was accomplished by posing and answering the following three questions regarding asbestos exposures: 1) Was the American Conference of Governmental Industrial Hygienists’ (ACGIH) 5 million particles per cubic foot (mppcf) of air threshold limit value, in effect for many years, a total dust standard? 2) Does the presence of visible dust indicate the presence of more than 5 mppcf of dust in the air? 3) Would the presence of visible asbestos-containing dust demonstrate a potential health hazard? The author conducted a review of the available literature to determine the answers to these questions. The author also extensively researched and analyzed the conversion factor or ratio between exposures in units of mppcf and f/cc. The results indicate that: i) the 5 mppcf asbestos standard was based on total dust, not just asbestos dust; ii) the presence of visible dust from ACM operations is likely greater than 5 mppcf; and iii) that the presence of visible asbestos-containing dust likely results in levels above the American Conference of Governmental Industrial Hygienists’ (ACGIH) and the Occupational Safety & Health Administration’s (OSHA) standards. These results have implications for individuals performing retrospective asbestos exposure analysis.

Experience Oneness with Creation: The Pathway to Universal Consciousness

Experience Oneness with Creation: The Pathway to Universal Consciousness

Contributions of pioneering women in indoor environment and health.

Contributions of pioneering women in indoor environment and health.

A long story short.

A long story short.

For God and Gaga: Comparing the Same-Sex Marriage Discourse and Homonationalism in Canada and the United States

For God and Gaga: Comparing the Same-Sex Marriage Discourse and Homonationalism in Canada and the United States

Inexpensive cleanroom for microfabrication, microarray work, and other activities requiring protection from airborne contamination.

Microfabricated devices includingmicroarrays and microfluidic systemsare subjects of increasing interest in avariety of fields (1). The production ofthese devices requires protection fromairborne contamination. Ideally, suchwork is best carried out in a cleanroomfacility, but conventional cleanroomconstruction can cost several hundreddollars per square foot. A less expensivealternative is the “softwall” cleanroom.A softwall clean room is simply a metal-framed tent of heavy vinyl curtains thatis continuously supplied with filtered airat the top. The air exits at the bottom viaa gap between the curtains and the floor.This type of cleanroom is commerciallyavailable from several manufacturersand can be installed in almost any kindof open room space. Typically, the topsof these rooms consist of lighting mod-ules and high-efficiency particulate filtermodules. ISO class 100, 1000, and10000 rooms are available (the numberindicating the average particle count percubic foot of air), with more filter unitsused per square foot of floor area toachieve cleaner conditions. A lightedsoftwall cleanroom costs on the order of$100 per square foot.We present here a construction de-sign whereby we produced a softwallcleanroom ourselves at a materials costof approximately $10 per square foot(excluding labor) (2). Key to the lowcost was the use of existing room light-ing via transparent ceiling panels inplace of expensive cleanroom lightingfixtures and the use of a new consumerproduct air cleaner unit that has recent-ly become available for use in wood-working shops. This type of filter unitis specified to move 850 cubic feet perminute of air with up to 98% efficiencyin removing 5-µm particles and up to85% efficiency in removing 1-µm par-ticles (Delta International MachineryData Sheet for Model 50-860 AirCleaner, http://www. deltamachinery.com). As a consumer product, the costof these air cleaner units is much lowerthan the cost of conventional clean-room filter units. The relatively easyand inexpensive method described hereto produce a cleanroom environmentshould facilitate wider participation inthe recent expansion of research involv-ing microfabricated devices.Figure 1 shows a drawing of the 6 ×10-foot softwall cleanroom constructedin this laboratory. The frame was fabri-cated from locally purchased standardsteel material using 2 ×2 ×1/8-insquare tubing for the posts and 2 ×4 ×1/8-in rectangular tubing for the hori-zontal beams. The corner joints wereformed by attaching 10 ×10 ×1/8-inthick triangular steel plates to the postsand beams with 3/8-24 machine screwsvia threaded holes in the beams.The sides of the frame were coveredwith curtains of 0.04 in transparentpolyvinyl chloride (PVC, cut from 54-inwide roll material; AIN Plastics, Mariet-ta, CA, USA) attached to the beams with10–24 machine screws and washers. Thecurtains were overlapped 6 in at theedges (no sealing was required; the ma-terial “sticks” to itself), and a 6-in gapwas left between the bottom of the cur-tains and the floor. A 2 ×4-foot entrancevestibule (under the air cleaner unit inFigure 1) was formed in the corner ofthe enclosure with additional PVC cur-tains and fitted with a “sticky mat”(Fisher Scientific, Pittsburgh, PA, USA).Air was not supplied to this vestibule.Passages were provided in the ends ofthe vestibule as overlapped joints be-tween two curtain pieces. The entrancevestibule provides a place for the opera-tor to put on cleanroom apparel (haircover, frock, and shoe covers; KapplerUSA, Guntersville, AL, USA) beforeentering the cleanroom.The top of the enclosure was framedwith standard ceiling grid material(Armstrong World Industries, Lancast-er, PA, USA) screwed to the beams in apattern to accept 2 ×4-foot transparentacrylic ceiling panels (ICI Acrylics,Cordova, TN, USA), which were held

Utility Perspective of Selecting Air Filter for Simple-Cycle, Heavy-Duty Combustion Turbines

The combustion turbines evaluated for this study range in size (nominal) from 80 MW to 100 MW and operate at a compression ratio between 10 and 14. Under these conditions the compressor ingests about 500,000 to 725,000 cubic feet of air per minute for its rated output. With this volume of air, even low concentrations of contaminants can result in a significant total amount of contaminants entering the unit, which may cause compressor erosion, fouling, and foreign object damage in the compressor section and cooling air passage blockage, locking of turbine blade roots, and hot corrosion or sulfidation in the turbine section. Adequate protection against the above-mentioned degradation or damage due to poor air quality may be obtained by using properly designed air filters. An inadequate filter system or total lack of one results in a reduction in power and efficiency over the life of the unit and may significantly decrease the intervals between maintenance and thereby increase the cost of maintenance. Consideration should be given to adding an air inlet filter when or after the combustion turbine without air filter is overhauled to reduce future maintenance costs. This study investigates the need for an inlet air filtration system for simple-cycle, heavy-duty combustion turbines from a cost/benefit and operation standpoint. Options for inlet air filters include a self-cleaning pulse type filter, a surface loading cartridge filter without pulse feature, and a three-stage depth loading type media type filter. Benefits are determined by estimates of improvements in performance and effects on the combustion turbine’s longevity and maintenance.

A STATISTICAL ANALYSIS OF THE PERFORMANCE OF MILKING SYSTEM VACUUM REGULATORS

Milking machine vacuum regulators were tested at dairies across the United States over a period of twelve years. The drop in vacuum level with increasing air flow for each regulator tested was modeled using segmented regression. Three measures of regulator performance were considered: the slope of the line in the first phase, the variability about the first line, and the join point (after which vacuum pressure began to drop rapidly). The distribution of the join point was estimated based on an accelerated failure time model with censoring, Weibull errors, a model effect, and a linear effect of set point vacuum. For each model, the average slope of the first line, the average variability about the line of the first regime, and the estimated median cfm (cubic feet of air per minute, New Zealand standard) for a join point with set point vacuum of 13 in. Hg were standardized. These standardized values were used in a cluster analysis to identify four performance groups of regulator models.

Characterization of Worker Exposures to Methylene Chloride Resulting from Application of Aerosol Glue in the Asbestos Abatement Industry

Abstract Adhesives containing large percentages of methylene chloride are commonly utilized in the asbestos abatement industry. The adhesive is used to seal polyethylene sheeting to the underlying surfaces, which in turn is used to contain the work area. When completely contained, the work area is essentially a confined space. During subsequent asbestos removal procedures, High Efficiency Particulate Air filter (HEPA)-equipped exhaust systems provide dilution ventilation to the work area, exhausting 1000 to 2000 cubic feet of air per minute per machine. This study characterizes worker exposure levels to methylene chloride when applying these adhesives during the construction of asbestos abatement containments. Personal samples were collected with both 3M organic vapor monitors and standard SKC charcoal tubes. Analysis of the sampling media was conducted by gas chromatography according to NIOSH Method 1005. Exposure periods, ranging from four to six hours, corresponded to a personal time-weighted average (TWA) of 0.09 to 270 ppm. This corresponded to an eight-hour TWA range from 0.06 to 140 ppm, respectively. Short-term exposure limits (STEL), 15 minutes in duration, ranged in concentration from non-detectable to 1294 ppm. Exposure concentrations greatly varied depending upon dilution ventilation, exposure period, adhesive quantity, and room volume. Sample results revealed that use of large quantities of adhesive in a confined area can result in high concentrations of methylene chloride. It is recommended that the HEPA-equipped exhaust systems, primarily designed to control airborne asbestos fiber levels during subsequent removal procedures, be utilized to provide dilution ventilation to the work area when applying these adhesives. It is a current Environmental Protection Agency and Occupational Safety and Health Administration recommendation to start the HEPA-equipped exhaust systems after the work area is completely sealed off and the decontamination unit has been constructed. If these systems are activated at the beginning of the preparation phase, they will create dilution ventilation that can decrease methylene chloride concentrations by a minimum of fourfold. In addition, air purifying respirators equipped with organic vapor cartridges or supplied air respirators should be worn by the workers to reduce their exposure levels even more. Finally, the aerosol manufacturers should substitute the methylene chloride in these products with a suitable, less toxic replacement.

Nosocomial tuberculosis.

Hospital employees are at risk of contracting tuberculosis from patients. The undiagnosed case with sputum-smear positive for acid-fast bacilli is the usual source case. However, even the smear-negative patient may pose a risk. This was documented by a high rate of skin test conversion in hospital staff exposed to a smear-negative, culture-positive patient in a respiratory intensive care unit. The patient required bronchoscopy, intubation, and assisted ventilation. Of susceptible hospital staff members who were exposed to the index case, 14 of 45 (31%) converted their PPD skin test. Ten of 13 (77%) susceptible hospital staff members present at the time of bronchoscopy converted, compared with 4 of 32 (12.5%) who were not present at bronchoscopy (Fischer's exact test p = 0.0006). Rough calculations suggest that during the bronchoscopy and intubation the index case generated at least 249 infectious units per hour. At the ventilation levels in this area, this resulted in 1 infectious unit of tuberculosis in each 68.9 cubic feet of air. Improved ventilation, high efficiency filters, and ultraviolet irradiation are effective recommended ways to clean the air of infectious particles.

Group B streptococcal lung infection in neonatal rabbits.

The interaction of alveolar macrophages (AMs) and group B streptococci (GBS) was investigated in 1 and 2-day-old rabbits following infection in an exposure chamber containing 10(7) streptococci per cubic foot of air. The % of streptococci within AMs was similar at 0 and 4 h (36 and 65%) after infection for the two groups of rabbits. Twenty-four h after infection, the 2-day-old rabbits had a significantly higher % of ingested GBS (86 versus 68%). Sixty % of inspired GBS were inactivated by the older rabbits within 4 h after infection. This clearance persisted in the younger rabbits until 48 h (mean negative clearance of -17, -276, and -79% at 4, 24, and 48 h) before their numbers were reduced by inflammation. Sixty of 78 1-day-old rabbits had inflammatory responses between 24 and 72 h versus only 5 of 50 older rabbits. At 24 h after infection, AMs of 1-day-old rabbits contained significantly increased numbers of intracellular GBS microcolonies (17/20) than did AMs from 2-day-old rabbits (5/19). These observations suggest that the enhanced susceptibility to GBS infection in the immediate postnatal period is caused at least in part by ineffective intracellular killing by AMs.

Chute-Hydropulping Waste Disposal System: A Reservoir of Enteric Bacilli and Pseudomonas in a Modern Hospital

This report details an investigation of a significant increase in nosocomial gramnegative bacteremia caused by enteric bacilli and Pseudomonas aeruginosa. The chute-hydropulping waste disposal system was identified as a bacteria-rich reservoir, with 108 enteric bacilli and P. aeruginosa per gram of pulp. The system was found to be a gross source of airborne fecal flora. Airborne dissemination of a virus by that system was documented, and other viruses and infective agents of human disease might have been introduced from the waste pulp through the 16-story chute into the patients' ecosystem. Closure of the waste disposal complex resulted in disappearance of enteric organisms and P. aeruginosa from the hospital air. Average colony counts declined from > 150 to 40 per cubic foot of air. The incidence of nosocomial septicemia caused by P. aeruginosa and other gramnegative organisms declined concomitantly and continued at a reduced rate throughout a 19-month follow-up. Even though the evidence is circumstantial, it is urged that hospital designers prevent the described sources of gross contamination and nosocomial hazards.

Wire and Litter Management Systems for Broiler Breeders

Three wire pens, each with 250 female broiler breeders and 25 Cornish type males housed a 1 sq. ft. per bird, were compared with three litter floor pens each having 150 females and 15 males at 3 sq. ft. per bird.Egg production and mortality were significantly higher in wire houses than in litter floor houses. Hatchability of fertile eggs were similar in both management systems during the 28 week test. Fertility was significantly different as it averaged 9.2% lower in wire floor houses. The fertility difference gradually increased from the second through the seventh four week periods and was believed to be related to an increasing problem of sore feet of the cockerels on the wire floor.Counts of air bacteria, air fungi and bacteria on the egg were all significantly higher in the litter floor houses than in the wire floor houses. The mean bacteria count per cubic foot of air was 2.2 times greater in the litter houses while there was 10 times more bacteria found on the shells of eggs from the litter floor houses. The relationship of these differences in microbe counts to chick contamination rates was not established.

Survey of a Laboratory Building for Airborne Antibiotics

Antibiotics are routinely examined by laboratory analysis in a six-story building which houses the laboratories of the National Center for Antibiotics and Insulin Analysis (NCAIA) on the second floor. A survey was performed to determine if antibiotic dust was being disseminated throughout the building. Air throughout the building was analyzed both quantitatively and qualitatively for residues of penicillin and tetracyclines. The microbiological assay plates used were sensitive enough to detect 0.001 unit of penicllin and 0.0004 mcg. of chlortetracycline in the air. Results of this study showed that, outside of the actual laboratories of NCAIA, the incidence of antibiotic contamination of the air was negligible. In the immediate areas where antibiotics were physically handled, 0.012 unit of penicillin and 0.0185 mcg. of chlortetracycline per cubic foot of air were detected.

Application of Anderson sampler in studying airborne fungi in San Antonio, Texas.

A quantitative study of airborne fungi in the San Antonio area has been conducted for a period of ten weeks (October-December, 1969) with the use of the Anderson sampler. One day a week one cubic foot of air was sampled four times: 8 A.M., 12 A.M., 4 P.M., and 8 P.M.Hormodendrum, Alternaria andStemphylium were the most prevalent fungi encountered, followed byPenicillium, Fusarium andAspergillus. The morning sampling (8 A.M.) produced the least amount of colonies on the plates, while the evening sampling (8 P.M.) produced the highest. Furthermore, the highest colony count was experienced during the first half of October, while the lowest appeared during the last part of November. According to this survey, there appears to be no significant correlation between the time of the day or month and the percentage of the various species of airborne fungi found in this vicinity.

Odor Transport by Particulate Matter in High Density Poultry Houses

MODERN commercial high density poultry houses contain high concentrations of airborne particulate matter. Concentrations as high as 1.16 mg. per cubic foot of air have been reported (Anderson et al., 1966). This concentration is twenty-five times greater than the maximum reported in urban atmospheres (Wolfe et al., 1967). Smith and O’Meara (1965) found that the concentration of particulate matter in a poultry house was related to the bodily activity of the birds; the greater the activity, the greater the concentration of airborne particulates. The particulate matter consists of fecal matter, feed particles, as well as feather and epidermal fragments (Koon et al., 1963; and Smith and O’Meara, 1964).Day and Lebeda (1964) found that particulate matter collected from the atmosphere of a swine confinement building was odoriferous. Gas chromatographic analyses were performed on an extract of the dust. Several very volatile, low molecular weight compounds were found. These were not…

Particle size distribution of Serratia marcescens aerosols created during common laboratory procedures and simulated laboratory accidents.

Andersen air samplers were used to determine the particle size distribution of Serratia marcescens aerosols created during several common laboratory procedures and simulated laboratory accidents. Over 1,600 viable particles per cubic foot of air sampled were aerosolized during blending operations. More than 98% of these particles were less than 5 mu in size. In contrast, 80% of the viable particles aerosolized by handling lyophilized cultures were larger than 5 mu. Harvesting infected eggs, sonic treatment, centrifugation, mixing cultures, and dropping infectious material produced aerosols composed primarily of particles in the 1.0- to 7.5-mu size range.

Comparison of microbial contamination levels among hospital operating rooms and industrial clean rooms.

Microbial contamination in industrial clean rooms was compared quantitatively and qualitatively with that of hospital operating rooms. The number of aerobic mesophilic microorganisms which accumulated on stainless-steel strips exposed for periods up to 21 weeks to the intramural air of four operating rooms was at least 1 log higher than the accumulation on strips exposed in four clean rooms, and was essentially the same as that found in two factory areas. Volumetric air samplings showed that there were significantly higher numbers of airborne viable particles per cubic foot of air in operating rooms than in industrial clean rooms. In contrast to clean rooms, where most of the airborne contaminants were those associated with human hair, skin, and respiratory tract, the hospital operating rooms showed a very high level of microorganisms associated with dust and soil.

Comparison of Microbial Contamination Levels Among Hospital Operating Rooms and Industrial Clean Rooms

Microbial contamination in industrial clean rooms was compared quantitatively and qualitatively with that of hospital operating rooms. The number of aerobic mesophilic microorganisms which accumulated on stainless-steel strips exposed for periods up to 21 weeks to the intramural air of four operating rooms was at least 1 log higher than the accumulation on strips exposed in four clean rooms, and was essentially the same as that found in two factory areas. Volumetric air samplings showed that there were significantly higher numbers of airborne viable particles per cubic foot of air in operating rooms than in industrial clean rooms. In contrast to clean rooms, where most of the airborne contaminants were those associated with human hair, skin, and respiratory tract, the hospital operating rooms showed a very high level of microorganisms associated with dust and soil.

Particle Size Distribution of Serratia marcescens Aerosols Created During Common Laboratory Procedures and Simulated Laboratory Accidents

Andersen air samplers were used to determine the particle size distribution of Serratia marcescens aerosols created during several common laboratory procedures and simulated laboratory accidents. Over 1,600 viable particles per cubic foot of air sampled were aerosolized during blending operations. More than 98% of these particles were less than 5 mu in size. In contrast, 80% of the viable particles aerosolized by handling lyophilized cultures were larger than 5 mu. Harvesting infected eggs, sonic treatment, centrifugation, mixing cultures, and dropping infectious material produced aerosols composed primarily of particles in the 1.0- to 7.5-mu size range.