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PubMed1979

Respirator use and protection from exposure to carbon monoxide.

Investigations of the protective effect afforded by respirators in Baltimore firefighters are presented. The data indicates that the continuous use of respirators offers significant protection from exposure to carbon monoxide but that this protection is not absolute. A surprising finding is that the intermittent use of the face mask offers as little protection to the men as does non-use. These findings emphasize the difficulties in relying upon respiratory personal protective equipment for protection from exposure.

Adult↗
PubMed1979

Respirator cartridge test system and test results for benzene and acrylonitrile.

NIOSH approves organic vapor respirator cartridges based upon testing against 1000 parts per million carbon tetrachloride vapors. Data for other organic vapors are necessary for proper use of organic vapor cartridge respirators against those vapors. This paper describes a system designed to test respirator cartridges and canisters and results of cartridge tests against benzene and acrylonitrile at a variety of concentrations.

Acrylonitrile↗
PubMed1979

The efficiency of respiratory filters in a coke oven atmosphere.

Several types of commercially available respiratory filter/sorbent combinations were tested in a coke oven environment. The percent penetration of benzene soluble particulate and benzo(a)pyrene through these filters was determined and was generally found to be less than ten percent. Degradation of filtering efficiency was noted with some types of filters. The use of a sorbent cartridge in conjunction with a covering filter did not significantly change penetration of the contaminants which were measured.

Analysis of Variance↗
PubMed1980

Inhalation exposure of cadmium workers: effects of respirator usage.

The objective of this study was to determine the average reduction in inhalation exposures produced by intermittent use of filter cartridge respirators by cadmium workers. Inhalation exposure was estimated by measuring the cadmium concentration inside the respirator while it was worn or hanging around the worker's neck. Air concentrations of cadmium were measured simultaneously inside the respirator and at the worker's lapel with a dual sampling system. Each of nine workers were measured on three consecutive days for a full work shift. The average inhalation exposures ranged from 3 to 67 micrograms/m3 while the TWA lapel concentrations ranged from 19 to 3600 micrograms/m3; respirator use produced a substantial reduction in inhalation exposures when lapel concentrations were above 100 micrograms/m3. On the average, the inhalation exposure was 26% of the lapel concentration, but the effective protection varied widely between individuals and from day to day. If used cautiously, this relationship may be useful for estimating the approximate average inhalation exposure of a group of workers routinely using half mask respirators.

Air Pollutants↗
PubMed1983

Correlation of qualitative and quantitative results from testing respirator fit.

Three qualitative respirator fit tests were evaluated for their ability to adequately measure respiratory protection. The evaluated methods were the negative pressure test, the isoamyl acetate test, and the irritant smoke test. Each test was performed concurrently with a single quantitative fit test, the dioctylphthalate (DOP) test, during 274 half-mask and 274 full facepiece wearings. The quantitative values of DOP penetration obtained after passing or failing each qualitative fit test were lognormally distributed. For each qualitative test performed on each mask type, the average log penetration values obtained after passing and failing each test were statistically different from each other. The mean of the log penetration values associated with the failed qualitative test was always larger than the mean of the log penetration values associated with passed qualitative tests for all three qualitative methods. Most (95%) of the tested study had adequately fitting respirators as determined by quantitative testing. Of these subjects, 96% to 100% passed the qualitative fit tests. Of the 5% of the study subjects with inadequately fitting half mask respirators, 93% to 100% of the inadequate fits were detected by qualitative methods. Twenty three to 46% of the poorly fitting full face masks were detected by qualitative methods. The probability of passing or failing a qualitative test with an inadequately fitting respirator can be estimated; however, the uncertainty associated with each estimate is large due to the small number of study subjects with poorly fitting respirators.

Adult↗
PubMed1983

Computing partial-shift respirator use periods.

Occasionally, airborne contaminant concentrations cannot be reduced to desired levels, even after the installation of feasible engineering controls. The industrial hygienist may have to recommend full-shift or partial-shift use of appropriate respirators to reduce exposures. The method described allows the industrial hygienist to recommend the minimum period of time an exposed employee needs to use a respirator in order to reach the desired exposure level. The procedure is based on the calculation of Time-Weighted Averages, using the upper confidence levels of air sampling data, and the respirator protection factors.

Air Pollutants↗
PubMed1983

Do pressure-demand breathing systems safeguard against inward leakage?

Rescue operations conducted in toxic atmospheres require respiratory protective equipment capable of providing a very high degree of protection. A slight positive pressure in the facepiece throughout the breathing cycle is used in the pressure-demand, compressed-air breathing apparatus to eliminate any inward leakage. In the present work an inward leakage test with sulphur hexafluoride (SF6) was used to measure facepiece penetration in a pressure-demand system at different work loads. During the test, inspiratory-flow pressure variations within the facepiece and heart rate were also measured. Tests were performed on a dummy head and on two subjects. In some tests a poor face seal was introduced by putting an open tubing with an inner diameter of 2 mm and outer diameter of 3 mm under the sealing edge of the mask. It was found that inward leakage was less than 0.0001% under all conditions as long as facepiece pressure was positive. When facepiece pressure fell below zero, which occurred at inhalation peak flows about 300 L/min, an inward leakage was detected. One subject achieved, at extreme work load, an inhalation peak flow around 450 L/min. These results show that pressure-demand systems should be tested with a breathing machine giving peak flows of at least 300 L/min to ascertain the capability of these systems to maintain positive pressure in the facepiece during hard rescue work.

Adult↗
PubMed1983

The effect of the growth of facial hair on protection factors for one model of closed-circuit, pressure-demand, self-contained breathing apparatus.

Protection factors for one model of closed-circuit, pressure-demand, self-contained breathing apparatus were determined for eight volunteers while clean-shaven and at approximately two-week intervals during an eight-week, beard-growth period. Measurement of facepiece leakage was patterned after the DOP quantitative fit test method outlined in ANSI Z88.2-1980. Comparison of results indicated that beard growth had a profound adverse effect on the amount of protection provided.

Analysis of Variance↗
PubMed1983

Common materials for emergency respiratory protection: leakage tests with a manikin.

In areas where respirators are not routinely used, emergencies (such as fires) may occur in which protection from airborne particles is necessary. The following readily available materials were tested on a manikin connected to a breathing simulator to determine the fraction of an approximately 2-micron diameter aerosol that would leak around the seal between the materials and the manikin's face: cotton/polyester shirt material, cotton handkerchief material, toweling (a wash cloth), a surgical mask (Johnson & Johnson Co., Model HRI 8137), and a NIOSH-approved disposable face mask (3M Corp., Model #8710). The leakage tests were done to supplement the measurements of penetration through the materials reported previously. Leakage fractions were determined by comparing the penetration of the same aerosol for the materials held to the face versus being fully taped to the face. At a breathing rate of 37 liters per minute, mean leakages for the materials ranged from 0.0 percent to 63 percent, depending on the material. Mean penetrations exclusive of leakage ranged from 0.6 percent to 39 percent. Use of nylon hosiery material ("panty hose") to hold the handkerchief material or the disposable face mask to the face was found to be very effective in preventing leakage. Such a combination could be expected to reduce leakage around the handkerchief to about 10 percent or less in practice, and around the mask to less than one percent, which suggests the adaptation and use of such an approach for industrial hygiene.

Dust↗
PubMed1983

Inhalation exposure of lead in brass foundry workers: the evaluation of the effectiveness of a powered air-purifying respirator and engineering controls.

The protection that a powered air-purifying respirator afforded to ladle and furnace attendants who were exposed to lead, copper and zinc fumes in a brass foundry was found by measuring metal levels at the lapel and at nose level inside the respirator. Respirator fit was evaluated by use of a hot-wire anemometer at the face/Tyvek seal interfaces, and at the exit of the respirator. Effective protection factors for lead ranged from 1.05 to 67. Ergonomic factors and engineering controls are also discussed.

Air Pollutants, Occupational↗
PubMed1983

Critical review of international standards for respiratory protective equipment - I. Respiratory protective equipment for particulate-laden atmospheres.

The standards for respiratory protective equipment (R.P.E.) from eleven countries and standards organizations were grouped according to type as particulate removing, gas and vapor removing, airline (fresh air hose and compressed air types), and self-contained breathing apparatus (open circuit and closed circuit). Each group of standards was further divided into specification and performance requirements. This paper is one in a series of three that highlights and critically reviews international respirator standards; it deals specifically with R.P.E. for protection against particulate-laden atmospheres. Great Britain, Australia, European Committee for Standardization (CEN), France, South Africa, Italy, Spain, New Zealand, Scandinavia, Japan, and Germany have standards for R.P.E. against particulate-laden atmospheres. Tabular summaries and accompanying discussion of national requirements are presented in the following categories: solid and liquid aerosol removal efficiency, clogging, and rough usage. Large differences and some notable omissions exist among standards. For example, the protection capacity of the filter can be tested by using solid particulate or liquid challenge aerosols. The majority of the countries evaluate protection capacity using solid particulate aerosols, while the remainder use both solid and liquid or liquid aerosols only. Other differences in filter testing deal with the composition of the test aerosol and the characteristic of the filter measured. The initial penetration or the penetration of the filter as it is being loaded over a specified period of time can be measured. In the latter case penetration is averaged over the test period and the degree of protection is assessed only for that overall time period; information is not provided concerning the protection afforded by the filter in the earlier stages of use.

Aerosols↗
PubMed1983

Critical review of international standards for respiratory protective equipment - II. Gas and vapor removal efficiency and fit testing.

The purpose of a Respiratory Protective Equipment (R.P.E.) standard is to assure that a minimum level of performance is reached by the respirator. Standards from a number of countries and standards organizations require that certain specifications are met in construction and that respirators be evaluated by specific performance tests. This is the second of three critical review papers related to respirator standards. We here summarize in tabular form, compare and critically review how the different countries or standards organizations test respirators designed for protection against gases and vapors for leakage due to improper fitting of the respirator facepiece and gas and vapor removal efficiency of the cartridge/canister. Two general aspects as they relate to removal capacity testing are discussed. The first issue deals with the selection of test gases and vapors that best represent the sorptive behavior of a class or group of compounds. The second issue deals with the extrapolation of laboratory testing under rigidly specified conditions to conditions of actual use. Fit testing varies from country to country. The fit testing conditions specified in the various standards are summarized along with a discussion of test material selection, the test panel selection, and the range of controlled test activities.

Air Pollutants, Occupational↗
PubMed1983

Critical review of international standards for respiratory protective equipment - III. Practical performance tests.

This paper, the third in a series of papers devoted to review of international standards for Respiratory Protective Equipment (R.P.E.), summarizes in tabular form, compares, and critically reviews standards of different countries or organizations pertaining to practical performance tests (Man Tests). There are similarities, differences and omissions in the national standards that deserve attention. Of the countries or organizations that require Man Tests on particulate and/or gas and vapor respirators, none described in detail the tests to be performed. For example, CEN requires that Man Tests be conducted on gas/vapor respirators under realistic conditions to determine imperfections that cannot otherwise be determined by other performance tests, but does not stipulate the testing procedure. With respect to fresh-air hose, compressed-air line and self-contained breathing apparatus R.P.E., only Great Britain and CEN present specific Man-testing requirements in detail. Man Tests for all types of R.P.E. have a specific purpose: to determine any imperfections in, or malfunction of the apparatus under simulated work conditions. One major difference, however, is in the kind of work simulation activities required. In the testing of fresh-air hose and compressed-air line respirators, for instance, CEN describes in great detail, a variety of activities to be conducted. Great Britain merely states that the subjects shall work in practical conditions. Another important disparity relates to the conditions under which the test is to be performed. For example, CEN requires a heavy-duty test and a cooled chamber test, as well as tests under normal and low temperature conditions. Great Britain, on the other hand, requires only the latter two tests. Still other differences lie in the kinds of medical surveillance required during testing and the evaluation criteria used for assessment.

Air Pollutants, Occupational↗
PubMed1984

Effect of facial hair on the face seal of negative-pressure respirators.

The effect of facial hair on the face seal of negative-pressure respirators, both half-masks and full facepieces, has been investigated. Three hundred and seventy (370) male employees were fit tested both qualitatively and quantitatively. Of these, sixty-seven (67) had fully established beards varying in length, shape, density and texture. Bearded subjects consistently failed the qualitative fit test protocol. Quantitative fit testing with half-mask respirators indicated that bearded employees had a median fit factor of 12 (8% leakage). A median fit factor of 2950 (0.03% leakage) was obtained on clean-shaven employees. An average two hundred and forty-six (246) fold drop in protection was experienced by bearded employees. With full facepiece respirators, the bearded employees had a median fit factor of 30 (3% leakage). A median fit factor of greater than 10 000 (less than 0.01% leakage) was obtained on clean-shaven employees. At least a three hundred and thirty (330) fold drop in protection was experienced by bearded employees. Results indicate that the presence of a beard greatly increases the leakage through the respirator face seal, and this leakage should not be permitted when employees are required to wear respirators.

Face↗
PubMed1984

Airborne isocyanates in polyurethane spray painting: determination and respirator efficiency.

The concentrations of airborne isocyanates were measured during spray painting with two-component polyurethane paint. The isocyanate component - hexamethylene-diisocyanate (HDI) and its prepolymer of the biuret type - were determined by high performance liquid chromatography after derivatization to stable urea derivatives with N-4-nitrobenzyl-N-n-propylamine. Samples were collected on reagent impregnated glassfiber filters, and the derivatives were eluted with the chromatographic eluent. An impregnation technique is reported; it facilitates the chromatographic separation and the subsequent quantitative determination. Recovery studies from filters were performed in the range of 0.05 to 30 micrograms for the HDI monomer, and 0.5 to 100 micrograms for the HDI oligomer on the same filter. Average recoveries of the monomer and the oligomer were 97 +/- 2% (standard deviation) and 92 +/- 4%, respectively. The concentrations of the isocyanate components, measured during spray painting, were very high. For example, the level of the monomer frequently exceeded the hygienic limit value of 0.07 mg/m, set by the National Board of Labour Protection in Finland. As the concentrations of the HDI oligomer were at least one order of magnitude higher, appreciable exposure to isocyanate occurred if the respiratory protection was inadequate. The filter sampling technique made it possible to measure concentrations inside respirators.

Air Pollutants, Occupational↗
PubMed1984

Some observations on frequency of respirator fit tests.

Quantitative respirator fit tests were repeated with workers who had demonstrated adequate fit initially. As the interval between first and second tests increased, it was expected that the rate of failure (penetration of test aerosol greater than 1%) on the second test also would increase. No significant time relationship was demonstrated, but the results suggest that the opposite of our expectation occurred: failure rates decreased with longer time intervals. If confirmed, the results suggest a simple strategy for repeat fit testing.

Humans↗
PubMed1984

Application of gas adsorption kinetics. I. A theoretical model for respirator cartridge service life.

Using the principles of gas adsorption kinetics, we have developed a new theoretical model addressing the adsorption and breakthrough of contaminant vapors or gases with respect to solid sorbents. Specifically, we have applied the theory to predict respirator cartridge service life in connection with individual contaminant exposure to toluene, vinyl chloride, ethyl acetate, and each of several different trichlorinated hydrocarbons at several levels of concentration. Theoretical expressions and contaminant breakthrough curves derived from our new approach are compared with those published previously by Mecklenburg and by Wheeler. The breakthrough curves derived by Mecklenburg and by Wheeler have approximately the same shape as the corresponding experimental curves for 0% to 40% breakthrough. However, these curves deviate in varying degrees from the experimental data at breakthrough values exceeding 40%. By contrast, our new theory agrees with published experimental results over the entire range of 0% to 100% breakthrough. The new model not only agrees with experimental observation, it is also less complicated and easier to apply to practical industrial hygiene problems than theories developed previously.

Adsorption↗