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At least 1,153 records · Page 64Linked to original sources
PubMed1984

Respirator evaluation for carbon setters with beards.

Studies of several types of disposable respirators were carried out in a prebake aluminum reduction plant to determine the protection factors associated with airborne particulates in the potroom environment. Seventy-five (75) individual tests of respirator performance were carried out on 60 different carbon setters during the actual carbon setting task. Acceptable performance was achieved with all types of respirators tested. There was no significant difference in respirator performance for employees with or without beards.

Aluminum↗
PubMed1986

Effectiveness of a positive pressure respirator for controlling lead exposure in acid storage battery manufacturing.

Effective protection factors for lead-acid storage battery manufacturing workers using powered air-purifying respirators and their corresponding blood lead histories are reported and compared with results for half-mask, negative pressure respirators. Airborne lead protection factors for the powered, air-purifying respirator ranged from 2 to 74, while lead levels in the blood remained stable or decreased for 8 of the 13 workers monitored when compared to negative pressure respirator use levels.

Air Pollutants, Occupational↗
PubMed1986

Laboratory evaluation of RDM-201 Respirable Dust Monitor.

The current paper discusses the results of laboratory experiments conducted to evaluate the GCA Respirable Dust Monitor RDM-201 in comparison with the standard Gravimetric Respirable Dust Sampler (GRDS). The samplers were compared in parallel within the atmosphere of an inhalation chamber laden with Arizona Fine Road Dust (AFRD). A wide range of dust concentrations (i.e., from 0.17 to 32:81 mg/m3) was used in the experiments. Sampling time varied from 15 to 120 min. There was a high agreement between the two GRDSs, particularly for samples with dust weight larger than 0.5 mg. The correlation and linearity between the RDM-201 display reading and the actual weight of dust on the instrument's filter were quite high for dust samples larger than 0.5 mg, but dropped significantly for samples less than 0.5 mg. Considering the extremely high dust concentration required to collect a minimum of 0.5 mg of respirable dust within 1-min sampling time of the RDM-201's automatic sampling mode, it was concluded that the use of automatic mode intended for quick evaluation of dusty atmosphere is impractical under most ordinary dusty conditions. The RDM-201 manual mode can be used, however, as reliably as a GRDS, for extended sampling times for assessment of TWAC of respirable dust in the atmosphere of a workplace, providing that a minimum of 0.5 mg sample is collected on the filter.

Air Pollutants, Occupational↗
PubMed1986

Determination of organic vapor respirator cartridge variability in terms of degree of activation of the carbon and cartridge packing density.

The protection provided by carbon-containing organic vapor respirator cartridges depends in part on the packing density of the carbon in the cartridges and its degree of activation. Large variations in these parameters could have significant effects on the service-life of respirator cartridges. Variability among commercially available organic vapor respirator cartridges was examined with regard to the following characteristics: the particle size distribution, amount of carbon and packing density of the carbon in the cartridges and the degree of activation of the carbon. The degree of activation was determined by measuring the maximum adsorption space and the structural constant of the carbon. These two parameters--Wo (cm3/g) and k (cal/M)-2--are constants in the Dubinin/Radushkevich (D/R) model from which physical absorption onto microporous adsorbents, such as activated carbon, are described. Respirator cartridges from three different suppliers were examined. Significant variability (11-40%) in the amount and the degree of activation of the carbon occurred between cartridges of different manufacturers, as well as among cartridges of an individual manufacturer.

Carbon↗
PubMed1987

Performance of dust respirators with facial seal leaks: II. Predictive model.

A performance model for half-mask and single-use respirators is presented. It represents a possible alternative to field measurements of respirator performance. Experimental data on filter and leak performance given in Part I were used to develop a model that allows one to predict 1) the overall respirator penetration as a function of particle size for any work rate and 2) overall total mass penetration for any work rate and exposure aerosol-size distribution for a known respirator filter and facial seal leak condition. A simplified method based on general regression equations is presented that allows one to estimate these quantities based on QNFT (quantitative fit testing) measurements and a knowledge of the exposure aerosol-size distribution. Example calculations are given for a situation in which QNFT gives a fit factor of 50 for a half-mask with dust, fume and mist filter cartridges, but predicted protection factors for various use conditions range from 20 to 81 depending on exposure particle-size distribution and work rate of the wearer.

Aerosols↗
PubMed1992

A theoretical model for respirator cartridge service life for binary systems: application to acetone/styrene mixtures.

A theoretical model, developed previously to assess respirator cartridge service life, was applied to various acetone/styrene binary assault systems. Experimental data, collected for several binary mixtures differing only with respect to the concentration of each of the two compounds, were interpreted in terms of the model. Styrene concentrations varied from 228 to 1578 ppm; the range of acetone concentrations was 92-985 ppm. The specific influence of the compound assault concentrations on respirator cartridge service life was carefully characterized, as break-through curves were generated for both acetone and styrene for each of several different binary systems. Specifically, experimental data for each system were used to determine values of the following theoretical parameters: k'1, tau 1, k'2, tau 2, and Am. These parameters were employed with the theory to generate complete theoretical breakthrough curves and to determine the time-dependence of the weight of each compound adsorbed by the respirator cartridge carbon bed. An interesting phenomenon observed for the acetone/styrene systems was the displacement (from the carbon) of previously adsorbed acetone molecules by styrene molecules. Acetone breakthrough was observed first in each of the systems studied. Following the onset of this breakthrough, the acetone breakthrough concentration was enhanced by the displacement of acetone from the carbon bed by the adsorption of styrene. The theoretical model accurately predicts both this enhancement and the associated breakthrough characteristics of styrene. In addition, the theory is capable of predicting the ratio of the number of displaced acetone molecules to the corresponding number of displacing styrene molecules. For these studies, this ratio ranged from 0.3 to 0.7. The service life of respirator cartridges exposed to acetone/styrene mixtures depends on the assault concentration of each compound and is significantly influenced (shortened) by the displacement phenomenon.

Acetone↗
PubMed1993

Deaths involving air-line respirators connected to inert gas sources.

During 1984 to 1988, the U.S. Occupational Safety and Health Administration (OSHA) investigated 10 incidents, with 11 fatalities, involving the inadvertent connection of air-line respirators to inert gas supplies. Seven deaths resulted from connecting an air-line respirator supply hose to a line which normally carried inert gas. Four deaths were caused by leakage or backfill of inert gas into a line which normally carried breathable air. Ten of the deaths were from nitrogen and one from argon. The circumstances of the 11 deaths indicated that coupling compatibility and supervisory oversight were major factors in the inappropriate supply of irrespirable gas to the respirators worn by these workers. Conscientiousness among safety personnel to the hazards of asphyxiation by inert gas, and compliance with current OSHA regulations, the ANSI Z88.2 standard, and NIOSH respirator certification approval regulations would have prevented these fatalities.

Accidents, Occupational↗
PubMed1993

Determining the service lives of organic-vapor respirator cartridges for nitroglycerin under workplace conditions.

Results of a field study that estimated the service lives of several different brands of organic-vapor respirator cartridges for nitroglycerin are presented. Respirator carbon tubes (RCTs) were used to sample in a workplace where gun powder was manufactured and where nitroglycerin levels varied from approximately 0.1-0.7 mg/m3. Tenax adsorbent tubes were used to monitor for nitroglycerin upstream and downstream of RCTs and were subsequently analyzed by a gas-chromatography method. A series of 10 trials failed to find evidence of nitroglycerin breakthrough. Estimates of the minimum service lives of respirator cartridges varied from 7-81 hours for nitroglycerin levels of 1.0 mg/m3, 10 times the current Occupational Safety and Health Administration Permissible Exposure Level. One trial specifically examined the potential of nitroglycerin to prematurely break through a cartridge due to bed migration, and results failed to indicate this as a potential problem. A field validation of the Tenax adsorbent tube method for nitroglycerin monitoring resulted in an accuracy of +/- 77-88% at the 95% confidence level. An unexpected finding was that up to 10% of the ambient nitroglycerin collected was adsorbed to an aerosol. This finding led to the recommendation that the addition of a prefilter to an organic vapor cartridge may be required when using air-purifying respirators to protect workers from some nitroglycerin exposures.

Equipment Failure↗
PubMed1995

The assigned protection factor of 10 for half-mask respirators.

A number of researchers have published or presented papers on workplace protection factor (WPF) studies involving halfmask respirators. Individually, each study contains a relatively small amount of data, generally less than 25 data points for any single respirator. Because of the small amount of data, any attempt to quantify the result statistically does not provide useful information on the low end of the distribution of WPFs. Several studies on half-mask respirators were combined to yield a data set with 390 observations. Of these WPF data, 1.5% were less than 10, the best estimate of the 5th percentile was 13, with a 95% confidence interval of 10 to 18. Differences between the mean WPF based on the type of filter were found, but no difference was found between the mean performance of elastomeric and disposable respirators equipped with dust/mist and dust/fume/mist filters.

Evaluation Studies as Topic↗
PubMed1996

Field performance measurements of half-facepiece respirators--foundry operations.

A series of field studies was conducted to measure workplace protection factors (WPF) provided by elastomeric and disposable half-facepiece respirators against different particulate contaminants. The research protocol developed for the study has been described in a previous article. This article presents results from dust and fume exposures at three foundries. The major components of the airborne exposures in these foundries were zinc, lead, and silicon. The major components of the in-facepiece samples were zinc, chlorine, and lead. Significant differences were observed in ambient zinc and lead concentration levels among foundries; however, no significant difference was observed in the in-facepiece concentrations of these elements among foundries. Respirator performance varied within each foundry, but there was no difference in performance when pooling all foundry data. The 5th, 10th and 50th percentile estimates for the pooled foundry and respirator WPF data were about 9, 16, and 114 respectively. The infacepiece concentration data clearly indicate that dust-fume-mist (DFM) class half-facepiece respirators, when conscientiously used, worn, and maintained, in conjunction with other existing controls in these foundries, provided effective worker protection.

Aerosols↗
PubMed1997

Sweat rate inside a full-facepiece respirator.

The accumulation of sweat inside a full-facepiece respirator mask and the rise in facial skin temperature can be important factors for acceptability of respirators worn in the heat. This study questioned how much sweat would have to be removed from a respirator (if a design to remove accumulated sweat were possible). Results from 20 subjects sitting in a warm, humid environment (35 degrees C and 90% relative humidity) for 90 minutes indicated that the average value was about 0.203 g sweat/min from the face, head, and neck, with most of that coming from the neck region. Men were found to have higher sweating rates than women. The results indicate that a large amount of sweat could accumulate inside the mask over a typical 8-hour day. Average facial skin temperature was found to rise about 2 degrees C over the 90-minutes test, and this rise could likely be the cause of the very uncomfortable rating given to the respirator.

Equipment Design↗
PubMed1998

Field performance measurements of half-facepiece respirators: developing probability estimates to evaluate the adequacy of an APF of 10.

To evaluate the protection provided by negative-pressure, half-facepiece respirators, ambient and in-facepiece samples were collected on workers in foundry, aircraft-painting, and steel-manufacturing operations. Protection was assessed by workplace protection factors (WPF). The appropriateness of the assigned protection factor (APF) for half-facepiece respirators was evaluated with a new approach using the WPF data from these and other studies previously published. The new approach utilizes binomial statistics based on the number of successes (no overexposure) and failures (overexposure) and is illustrated with a graphical representation of WPF data. With this consideration of the data, the probability of overexposure occurring during a wearing period for workers wearing the half-facepiece respirators represented by the studies referenced here was 0.5%, with a 95% confidence interval of 0.01 to 2.7%. If 50% in-facepiece sampling errors are considered, the probability of overexposure was 2.9%, with a 95% confidence interval of 1.1 to 6.3%. The authors believe the current APF of 10 for half-facepiece respirators is appropriate.

Air Pollutants, Occupational↗
PubMed2005

Head-and-face anthropometric survey of U.S. respirator users.

Sizing data generated by the military for use in fitting respirators have been the normative basis for commercial respirator sizing. Anthropometric data developed for males and females of military age in the 1950s and 1960s are still in use today and form the only comprehensive body of information available on this subject. The twofold objective of this study was to: (1) develop an anthropometric database detailing the face size distributions of respirator users using both traditional measurement methods and three-dimensional scanning systems; and (2) use the database to establish fit test panels to be incorporated into the National Institute for Occupational Safety and Health's respirator certification and international standards. A stratified sampling plan was used with three age strata, two gender strata, and four race/ethnic group strata. The plan called for an equal sample size of 166 in each cell. Subjects were obtained at 41 sites from 8 states. In addition to height and weight, 18 facial dimensions and neck circumferences were measured using traditional methods. A total of 3997 subjects were measured using traditional methods, and 1013 of them were also scanned using a 3-D head scanner. As this was a volunteer sample, subjects did not appear in the specific proportions needed for the sampling plan. The resulting data were weighted to correspond to the U.S. population. This article presents the summary statistics for the traditional measurement data only. Multivariate analyses of the data from this study and military data revealed that using historical, military data would be inadequate for describing the anthropometric variability of the current U.S. work force.

Adolescent↗
PubMed2006

A comparison of total, respirable, and real-time airborne particulate sampling in horse barns.

Measurements of total, respirable, and real-time airborne particulate were obtained in 12 horse barns in summer and winter. Respirable and total particulate concentrations were measured gravimetrically; real-time particulate was measured with an aerosol photometer. Total particulate (TP) ranged from nondetectable (ND) to 2.1 mg/m3 and from ND to 1.2 mg/m3 for winter and summer sampling, respectively. Respirable particulate (RP) ranged from ND to 0.2 mg/m3 and from ND to 0.7 mg/m3 for winter and summer measurements, respectively. The mean respirable fraction of particulate for summer and winter measurements was 0.63 and 0.34, respectively Real-time particulate (RTP) concentration was significantly correlated with TP for winter measurements and for pooled data but was not significantly correlated with RP for winter, summer, or pooled measurements. Peak, 10-sec average levels of RTP were estimated to range up to 22 mg/m3 in the samples collected. The data suggest that (a) airborne particulate concentrations and particle size distributions vary considerably among horse barns, and (b) real-time sampling, with an aerosol photometer, may be a more reliable measure of airborne TP than airborne RP in these environments.

Aerosols↗
PubMed2006

Integrated unit performance testing of powered, air-purifying particulate respirators using a DOP challenge aerosol.

Although workplace protection factor (WPF) and simulated workplace protection factor (SWPF) studies provide useful information regarding the performance capabilities of powered air-purifying respirators (PAPRs) under certain workplace or simulated workplace conditions, some fail to address the issue of total PAPR unit performance over extended time. PAPR unit performance over time is of paramount importance in protecting worker health over the course of a work shift or at least for the recommended service lifetime of the PAPR battery pack, whichever is shorter. The need for PAPR unit performance testing has become even more important with the inception of 42 CFR 84 and the recent introduction of electrostatic respirator filter media into the PAPR market. This study was conducted to learn how current PAPRs certified by the National Institute for Occupational Safety and Health would perform under an 8-hour unit performance test similar to the dioctyl phthalate (DOP) loading test described in 42 CFR 84 for R- and P-series filters for nonpowered, air-purifying particulate respirators. In this study, entire PAPR units, four with mechanical filters and one with an electrostatic filter, were tested using a TSI Model 8122 Automated Respirator Tester, with and without the built-in breathing machine. The two, tight-fitting PAPRs, both with mechanical filters, showed little effect on performance resulting from the breathing machine. The two loose-fitting helmet PAPRs indicate that unit performance testing without the breathing machine is a more stringent test than testing with the breathing machine under the conditions used. The PAPR with a loose-fitting hood gave inconclusive results as to which testing condition is more stringent. The PAPR unit equipped with electrostatic filters gave the highest maximum penetration values during unit performance testing.

Aerosols↗
PubMed1983

Long-term measurements of energy expenditure in humans using a respiration chamber.

There is a need to measure energy expenditure in man for a period of 24 h or even several days. The respiration chamber offers a unique opportunity to reach this goal. It allows the study of energy and nutrient balance; from the latter, acute changes in body composition can be obtained. The respiration chamber built in Lausanne is an air-tight room (5 m long, 2.5 m wide, and 2.5 m high) which forms an open circuit ventilated indirect calorimeter. The physical activity of the subject inside the chamber is continuously measured using a radar system based on the Doppler effect. Energy expenditure of obese and lean women was continuously measured over 24 h and diet-induced thermogenesis was assessed by using an approach which allows one to subtract the energy expended for physical activity from the total energy expenditure. Expressed in absolute terms, total energy expenditure was more elevated in the obese than in the lean controls. Basal metabolic rate was also higher in the obese than in the controls, but diet-induced thermogenesis was found to be blunted in the obese. In a second study, the effect of changing the carbohydrate/lipid content of the diet on fuel utilization was assessed in young healthy subjects with the respiration chamber. After a 7-day adaptation to a high-carbohydrate low-fat diet, the fuel mixture oxidized matched the change in nutrient intake. A last example of the use of the respiration chamber is the thermogenic response and changes in body composition due to a 7-day overfeeding of carbohydrate. Diet-induced thermogenesis was found to be 27%; on the last day of overfeeding, carbohydrate balance was reached by oxidation of 50% of the carbohydrate intake, the remaining 50% being converted into lipid.

Adult↗
PubMed2005

Evaluation of particulate filtering respirators using inward leakage (IL) or total inward leakage (TIL) testing--Korean experience.

Korean certification regulation for particulate filtering respirators requires inward leakage (IL) or total inward leakage (TIL) testing according to European Standard EN 13274-1, and the standard levels of compliance are similar to those of the European Standard. This study was conducted to evaluate particulate filtering respirators being commercially used in the Korean market using an IL or TIL test and the validity of standard level in Korea. Three half masks and 10 filtering facepieces (two top class, four 1st class and four 2nd class)-a total of 13 brand name respirators-were selected for the test with panels of 10 subjects. Each subject was classified with nine facial dimension grid squares in accordance with face length and lip length. IL or TIL testing was conducted at the laboratory of the 3M Innovation Center in which the experimental instruments and systems were established in compliance with European standards. The testing procedure followed EN 13274-1 (2001). As expected, leakages of half masks were less than those of filtering facepieces and the latter were significantly different among brands. TILs of the 1st class filtering facepieces were found to be much more than those of the 2nd class and the result may cause a wearer to get confused when selecting a mask. The main route leakage for filtering facepieces may not be the filter medium but the face seal. Therefore, it is necessary to develop well-fitting filtering facepieces for Koreans. Because leakages were significantly different for different facial dimensions, a defined test panel for IL or TIL testing according to country or race should be developed. A more precise method to demonstrate fit, for example, fit testing such as in the US regulations, will be needed before IL or TIL testing or when selecting a respirator. Another finding implies that geometric mean of five exercises for IL or TIL may be better than arithmetic mean to establish a standard individual subject mean.

Equipment Design↗
PubMed2003

Hybrid respiration in the denitrifying mitochondria of Fusarium oxysporum.

Induction of the mitochondrial nitrate-respiration (denitrification) system of the fungus Fusarium oxysporum requires the supply of low levels of oxygen (O(2)). Here we show that O(2) and nitrate (NO(3)(-)) respiration function simultaneously in the mitochondria of fungal cells incubated under hypoxic, denitrifying conditions in which both O(2) and NO(3)(-) act as the terminal electron acceptors. The NO(3)(-) and nitrite (NO(2)(-)) reductases involved in fungal denitrification share the mitochondrial respiratory chain with cytochrome oxidase. F. oxysporum cytochrome c(549) can serve as an electron donor for both NO(2)(-) reductase and cytochrome oxidase. We are the first to demonstrate hybrid respiration in respiring eukaryotic mitochondria.

Animals↗