Review of respirator performance testing in the workplace: issues and concerns

Respirators in Healthcare: Material, Design, Regulatory, Environmental, and Economic Considerations for Clinical Efficacy

Maintaining an ample supply of personal protective equipment continues to be a challenge for the healthcare industry, especially during emergency situations and times of strain on the supply chain. Most critically, healthcare workers exposed to potential airborne hazards require sufficient respiratory protection. Respirators are the only type of personal protective equipment able to provide adequate respiratory protection. However, their ability to shield hazards depends on design, material, proper fit, and environmental conditions. As a result, not all respirators may be adequate for all scenarios. Additionally, factors including user comfort, ease of use, and cost contribute to respirator effectiveness. Therefore, a careful consideration of these parameters is essential for ensuring respiratory protection for those working in the healthcare industry. Here respirator design and material characteristics are reviewed, as well as properties of airborne hazards and potential filtration mechanisms, regulatory standards of governmental agencies, respirator efficacy in the clinical setting, attitude of healthcare personnel toward respiratory protection, and environmental and economic considerations of respirator manufacturing and distribution.

Establishment of the key Technical Indicators of Positive Pressure Biological Protective Clothing

Objective

Trying to establish the key technical indicators related to positive pressure biological protective clothing (PPBPC), providing technical support for the establishment of PPBPC standards in the future.

Method

We examined the protection standard systems established by the major standards organizations in China and other developed countries. We also analyzed the technical indicators of the gas-tight chemical protective clothing and ventilated protective clothing against particulate radioactive contamination which closely related to PPBPC. And tested the performance of a set of imported dual-purpose PPBPC to verify the fit of its technical indicators with the standards. We aimed to identify the status of China’s standards in the area of personnel protection and put forward feasible suggestions for the production of PPBPC in China.

Results

Developed countries in Europe and North America have a complete system of standard protective clothing. China should also strengthen the construction of standard protective clothing, especially PPBPC.

Conclusion

With the improvements in infectious disease prevention and control on a global scale, the demand for PPBPC continues to increase and consideration should be given to the establishment of standards for this.

A novel approach to fit testing the N95 respirator in real time in a clinical setting

The instant measurements provided by the Portacount fit-test instrument have been used as the gold standard in predicting the protection of an N95 respirator in a laboratory environment. The conventional Portacount fit-test method, however, cannot deliver real-time measurements of face-seal leakage when the N95 respirator is in use in clinical settings. This research was divided into two stages. Stage 1 involved developing and validating a new quantitative fit-test method called the Personal Respiratory Sampling Test (PRST). In Stage 2, PRST was evaluated in use during nursing activities in clinical settings. Eighty-four participants were divided randomly into four groups and were tested while performing bedside nursing procedures. In Stage 1, a new PRST method was successfully devised and validated. Results of Stage 2 showed that the new PRST method could detect different concentrations and different particle sizes inside the respirator while the wearer performed different nursing activities. This new fit-test method, PRST, can detect face seal leakage of an N95 respirator being worn while the wearer performs clinical activities. Thus, PRST can help ensure that the N95 respirator actually fulfils its function of protecting health-care workers from airborne pathogens.

Studying the effectiveness of activated carbon R95 respirators in reducing the inhalation of combustion by-products in Hanoi, Vietnam: a demonstration study

BACKGROUND

Urban air pollution is an increasing health problem, particularly in Asia, where the combustion of fossil fuels has increased rapidly as a result of industrialization and socio-economic development. The adverse health impacts of urban air pollution are well established, but less is known about effective intervention strategies. In this demonstration study we set out to establish methods to assess whether wearing an R95 activated carbon respirator could reduce intake of polycyclic aromatic hydrocarbons (PAH) in street workers in Hanoi, Vietnam.

METHODS

In this demonstration study we performed a cross-over study in which non-smoking participants that worked at least 4 hours per day on the street in Hanoi were randomly allocated to specific respirator wearing sequences for a duration of 2 weeks. Urines were collected after each period, i.e., twice per week, at the end of the working day to measure hydroxy PAHs (OH-PAH) using gas chromatography/high resolution mass spectrometry. The primary endpoint was the urinary concentration of 1-hydroxypyrene (1-OHP).

RESULTS

Forty-four participants (54.5% male, median age 40 years) were enrolled with the majority being motorbike taxi drivers (38.6%) or street vendors (34.1%). The baseline creatinine corrected urinary level for 1-OHP was much higher than other international comparisons: 1020 ng/g creatinine (IQR: 604-1551). Wearing a R95 mask had no significant effect on 1-OHP levels: estimated multiplicative effect 1.0 (95% CI: 0.92-1.09) or other OH-PAHs, except 1-hydroxynaphthalene (1-OHN): 0.86 (95% CI: 0.11-0.96).

CONCLUSIONS

High levels of urine OH-PAHs were found in Hanoi street workers. No effect was seen on urine OH-PAH levels by wearing R95 particulate respirators in an area of high urban air pollution, except for 1-OHN. A lack of effect may be de to gaseous phase PAHs that were not filtered efficiently by the respirator. The high levels of urinary OH-PAHs found, urges for effective interventions.

TRIAL REGISTRATION

ISRCTN74390617 (date of assignation: 04/08/2009).

Real-time fit of a respirator during simulated health care tasks

Fit is an important but difficult-to-predict feature of respirator performance. This study examined a new approach to measuring respirator performance using two continuous direct-reading particle-counting instruments in a simulated health care workplace. A pilot test was conducted with eight experienced health care professionals who passed a traditional quantitative fit test before performing three randomized 10-min health care scenarios (patient assessment [PA], IV treatment [IV], and wound care [WC]). Two TSI Portacount Plus (Model 8020) with N95 Companion (Model 8095) instruments were used to continuously measure 1-sec ambient particle concentrations inside and outside the respirator facepiece. A simulated workplace protection factor (SWPF) was calculated by dividing outside by inside concentrations. Data were log transformed and examined using analysis of variance (ANOVA) between subjects, scenario types, and scenario order. The GM SWPF for the eight subjects, three scenarios per subject, ranged from 172 to 1073 (GSD 1.7 to 3.5) and was significantly different for each subject. A multi-way analysis of variance showed no difference between the three scenario types (PA, IV, WC). There were differences by the order in which scenarios were performed: the third scenario SWPF was significantly different and higher than that of the first and second scenarios. All subjects passed the initial quantitative fit test with a fit factor of at least 100. Five subjects had fit factors greater than 200 and GM scenario SWPFs greater than 400. Three participants with initial fit factors less than 200 had GM scenario SWPFs ranging from 132 to 326. This pilot test demonstrates that it is possible to evaluate instantaneous respirator fit using two quantitative fit test instruments in a simulated health care environment. Results suggest that an initial fit test may be predictive of fit during simulated tasks and that one scenario may be adequate for measuring a simulated workplace protection factor. [Supplementary materials are available for this article. Go to the publisher's online edition of Journal of Occupational and Environmental Hygiene for the following free supplemental resource: a video for subject D activities overlaid with simulated workplace protection factor data.].

Discomfort and exertion associated with prolonged wear of respiratory protection in a health care setting

The nature of discomfort and level of exertion associated with wearing respiratory protection in the health care workplace are not well understood. Although a few studies have assessed these topics in a laboratory setting, little is known about the magnitude of discomfort and the level of exertion experienced by workers while they deliver health care to patients for prolonged periods. The purpose of this study was to determine the magnitude of discomfort and level of exertion experienced by health care workers while wearing respiratory protection for periods up to 8 hr when performing their typical occupational duties. This project was a multiple cross-over field trial of 27 health care workers, aged 24-65, performing their typical, hospital-based occupational duties. Each participant served as his/her own control and wore one of seven respirators or a medical mask for 8 hr (or as long as tolerable) with interposed doffing periods every 2 hr. Self-perceived discomfort and exertion were quantified before each doffing: self-perceived level of discomfort using a visual analog scale, and self-perceived level of exertion using a Borg scale. Overall, and as would be expected, discomfort increased over time with continual respirator use over an 8-hr period. Interestingly, exertion increased only marginally over the same time period. The relatively low level of exertion associated with eight respiratory protective devices, including models commonly used in the U.S. health care workplace, is not likely to substantially influence workers' tolerability or occupational productivity. However, the magnitude of discomfort does appear to increase significantly over time with prolonged wear. These results suggest that respirator-related discomfort, but not exertion, negatively influences respirator tolerance over prolonged periods. Discomfort may also interfere with the occupational duties of workers.

Effect of fit testing on the protection offered by n95 filtering facepiece respirators against fine particles in a laboratory setting

OBJECTIVES

This study investigated particle-size-selective protection factors (PFs) of four models of N95 filtering facepiece respirators (FFRs) that passed and failed fit testing. Particle size ranges were representative of individual viruses and bacteria (aerodynamic diameter d(a) = 0.04-1.3 μm).

METHODS

Standard respirator fit testing was followed by particle-size-selective measurement of PFs while subjects wore N95 FFRs in a test chamber. PF values obtained for all subjects were then compared to those obtained for the subjects who passed the fit testing.

RESULTS

Overall fit test passing rate for all four models of FFRs was 67%. Of these, 29% had PFs <10 (the Occupational Safety and Health Administration Assigned Protection Factor designated for this type of respirator). When only subjects that passed fit testing were included, PFs improved with 9% having values <10. On average, the PFs were 1.4 times (29.5/21.5) higher when only data for those who passed fit testing were included. The minimum PFs were consistently observed in the particle size range of 0.08-0.2 μm.

CONCLUSIONS

Overall PFs increased when subjects passed fit testing. The results support the value of fit testing but also show for the first time that PFs are dependent on particle size regardless of fit testing status.

Preventing the soldiers of health care from becoming victims on the pandemic battlefield: respirators or surgical masks as the armor of choice

The respiratory protective equipment necessary to protect health care workers from the novel swine-origin influenza A (H1N1) virus is not known. The knowledge gap created by this unanswered question has caused substantial debate and controversy on a global scale, leading public health organizations to feel pressured into issuing decisive recommendations despite a lack of supportive data. Changes in clinical practice caused by public health guidance during such high-profile events can be expected to establish a new standard of care. Also possible is an unforeseen gradual transition to widespread N95 respirator use, driven by public health pressures instead of science, for all outbreaks of influenza or influenza-like illness. Therefore, public health organizations and other influential institutions should take care to avoid making changes to established practice standards, if possible, unless these changes are bolstered by sound scientific evidence. Until definitive comparative effectiveness clinical trials are conducted, the answer to this question will continue to remain elusive. In the meantime, relying on ethical principles that have been substantiated over time may help guide public health and clinical decisions.

Elastomeric, half-facepiece, air-purifying respirator performance in a lead battery plant

This workplace protection factor (WPF) study of a half facepiece air-purifying respirator with P100 filters was done in a lead battery manufacturing plant. Paired air samples for lead were collected inside and outside respirators worn by workers who were properly trained and quantitatively fit tested. Of the 45 valid sample sets, only four had detectable lead on the inside sample. WPFs were calculated for these sample pairs by dividing the outside sample lead concentration (C(o)) by the inside concentration (C(i)). For the remaining 41 sample pairs, the detection limit for lead was used to calculate a maximum estimated C(i) concentration. The C(o) for each of these sample pairs was divided by the C(i) estimate to obtain a minimum WPF value. All the WPFs were rounded down to two significant figures, resulting in values ranging from 12 to > 2500. A rank and percentile procedure resulted in a 50th percentile WPF of 270 and a lower 5th percentile estimate > 50. These WPFs exceed the assigned protection factor of 10 for half facepieces published by the Occupational Safety and Health Administration. This study's results support the APF of 10 and indicate the respirator provided appropriate protection as it was used in this study. The comparability of the two analytical methods commonly used together in WPF studies was also evaluated. The samples collected outside the respirators were analyzed for lead by proton-induced X-ray emission analysis (PIXE) followed by inductively coupled plasma spectrometry (ICP). While the two methods were highly correlated (r(2) = 0.965), the mean PIXE lead mass was approximately 45% higher than the mean ICP value. This systematic bias was explained by the assumptions used to interpret the PIXE analytical results. When WPF studies use ICP and PIXE for C(o) and C(i) samples, respectively, the calculated WPF values are conservative estimates of respirator performance.

Effect of protective filters on fire fighter respiratory health: field validation during prescribed burns

BACKGROUND

Bushfire smoke contains a range of air toxics. To prevent inhalation of these toxics, fire fighters use respiratory equipment. Yet, little is known about the effectiveness of the equipment on the fire ground. Experimental trials in a smoke chamber demonstrated that, the particulate/organic vapor/formaldehyde (POVF) filter performed best under simulated conditions. This article reports on the field validation trials during prescribed burns in Western Australia.

METHODS

Sixty-seven career fire fighters from the Fire and Emergency Services Authority of Western Australia were allocated one of the three types of filters. Spirometry, oximetry, self-reported symptom, and personal air sampling data were collected before, during and after exposure to bushfire smoke from prescribed burns.

RESULTS

Declines in FEV(1) and SaO(2) were demonstrated after 60 and 120 min exposure. A significant higher number of participants in the P filter group reported increases in respiratory symptoms after the exposure. Air sampling inside the respirators demonstrated formaldehyde levels significantly higher in the P filter group compared to the POV and the POVF filter group.

CONCLUSIONS

The field validation trials during prescribed burns supported the findings from the controlled exposure trials in the smoke chamber. Testing the effectiveness of three types of different filters under bushfire smoke conditions in the field for up to 2 hr demonstrated that the P filter is ineffective in filtering out respiratory irritants. The performance of the POV and the POVF filter appears to be equally effective after 2 hr bushfire smoke exposure in the field.

Workplace performance of a hood-style supplied-air respirator

This study evaluated the workplace performance of a hood-style supplied-air respirator during aircraft sanding operations. Air samples were collected inside and outside the respirators worn by workers during normal work activities. The samples were analyzed for chromium, strontium, and magnesium. These contaminants were not detected on any inside sample from the valid sample sets. Program protection factors (PPFs) were estimated for the valid sample sets using the limit of detection as the inside sample mass. When it was possible, PPF estimates were made using each element individually and a combination of all three elements. The PPF estimates were in the range of >11000 to >65000 regardless of the elements used in the calculation. Examination of the PPF estimates for different elements reveals the differences are largely artificial. The results indicate the tested respirator performed well above its assigned protection factor of 1000. No worker was overexposed to chromium, strontium, or magnesium during the study. This study also illustrates the difficulty in locating workplaces with sufficient contaminant concentration and duration to measure the capabilities of high-performing respirators.

Workplace protection factors for an N95 filtering facepiece respirator

This study evaluated the workplace performance of an N95 filtering facepiece, air-purifying respirator in a steel foundry. Air samples were collected inside and outside respirators worn by workers who were properly trained and qualitatively fit tested. For most workers, three or four pairs of air samples were collected on each of 2 days. The 49 valid sample sets were analyzed for iron, silicon, and zirconium. Only iron was present in sufficient concentrations to perform workplace protection factor (WPF) calculations. Individual WPF measurements ranged from 5 to 753. The geometric mean of the distribution was 119 with a lower 5th percentile value of 19. Time-weighted average WPFs (WPF(TWA)) were also calculated for each day for each worker as an estimate of the protection an individual might receive with daily respirator use. The WPF(TWA) values ranged from 15 for the worker with the single WPF value of 5, to a high of 684. The distribution of WPF(TWA) had a geometric mean of 120 and a lower 5th percentile of 22. Both data treatments indicate this respirator's performance was consistent with the assigned protection factor of 10 typically used for half facepiece respirators. The respirator provided adequate protection as used in this study. All contaminant concentrations inside the respirator were well below the relevant occupational exposure limits. Data collected also illustrate the dynamic nature of faceseal leakage in the workplace.

Effect of protective filters on fire fighter respiratory health during simulated bushfire smoke exposure

BACKGROUND

Bushfire fighters are potentially subject to risks from bushfire smoke. Although many different protective masks and filters are available, it is not clear which is the most effective from a health and safety perspective. The effect of protective filters on the respiratory health of Western Australian urban career fire fighters under controlled simulated conditions is investigated.

METHODS

Sixty-four healthy Fire and Emergency Services Authority of Western Australia (FESA) urban career fire fighters were subjected to controlled simulated bushfire smoke in an open smoke chamber for 15 min. The fire fighters were allocated one of the three types of protective filters: particulate only (P), particulate/organic vapor (POV), and a particulate/organic vapor/formaldehyde (POVF) filter using a double-blind randomized procedure. Personal air sampling inside the fire fighters' masks, spirometry, oximetry, and self-reported symptom data were collected at baseline and at two time intervals after the smoke exposure.

RESULTS

A significant decline in oxygen saturation was seen immediately after exposure, however, the decline was small and no significant relationships could be established between this and the type of filter used. A significantly higher number of participants in the P and POV filter groups self-reported an increase in coughing, wheezing, and shortness of breath compared to the POVF group. Air sampling demonstrated a significantly higher level of formaldehyde and acrolein inside the masks fitted with P filters compared to POV and POVF filters.

CONCLUSIONS

Testing the effectiveness of P, POV, and POVF filters under controlled conditions has demonstrated that the POVF filter provides statistically significant better protection for the fire fighters' airways in a simulated bushfire exposure chamber.

Respiratory protection from isocyanate exposure in the autobody repair and refinishing industry

This study, part of the Survey of Painters and Repairers of Auto bodies by Yale (SPRAY), evaluated the effectiveness of respiratory protection against exposure to aliphatic polyisocyanates. A total of 36 shops were assessed for respiratory protection program completeness; 142 workers were measured for respirator fit factor (FF) using PortaCount Plus respirator fit tester. Twenty-two painters from 21 shops were sampled using NIOSH method 5525 to determine the workplace protection factor (WPF) of negative pressure, air-purifying half-facepiece respirators equipped with organic vapor cartridges and paint prefilters during spray-painting and priming activities. Only 11 shops (30%) had written respiratory protection programs. Eighty percent of all fit tested workers passed the test on the first try with FF >or= 100, and 92% passed the second test after respirator use training. Overall geometric mean (GM) FF was 1012 for all fit tested workers. Significant differences on pass rate (92% vs. 72%) and on FF (1990 vs. 736) were found between previously fit tested workers vs. nontested workers. Twenty-nine WPF samples were collected. The outside facepiece GM concentration of total isocyanate group (NCO) was 378.4 micro g NCO/m(3) with 96% concentrations exceeding the U.K. short-term exposure limit, 70 micro g NCO/m(3), but no in-facepiece concentrations exceeded the limit. The GM WPF of total NCO was 319 (GSD 4) and the 5th percentile was 54. WPF of total NCO was positively correlated with the duration of painting task. FF positively correlated with WPF when FF was <or=450 but negatively correlated with WPF when FF was >450. We conclude that negative pressure, air-purifying half-facepiece respirators equipped with organic vapor cartridges and paint prefilters provide effective protection against isocyanate exposure in spray and priming operations if workers are properly trained and fitted.

Unipolar ion emission enhances respiratory protection against fine and ultrafine particles

We developed a novel concept that allows to considerably improve the performance of conventionally used filtering-facepiece respirators against fine and ultrafine aerosols including airborne viral and bacterial agents. The concept is based on the continuous emission of unipolar ions. The effect was evaluated through the real-time monitoring of the concentration and size distribution of fine and ultrafine aerosol particles. The measurements were conducted inside and outside of a respiratory mask that was face sealed on a breathing manikin. A commonly used Type N95 respirator and surgical mask were utilized for the tests. The manikin was placed in a 24.3-m³ indoor test chamber and exposed to polydisperse surrogate aerosols simulating viral and bacterial particles with respect to the aerodynamic size. The particle penetration through the mask was found to decrease by one-to-two orders of magnitude as a result of continuous unipolar ion emission in the chamber. The flux of air ions migrated to the breathing zone and imparted electrical charges of the same polarity to the aerosol particles and the respirator filter surface. This created an electrostatic shield along the external surface of the filter, thus enhancing the protection characteristics provided by the respirator. The above performance enhancement effect is crucial for minimizing the infectious risk in the cases when the conventional filtering-facepiece respirators are not able to provide an adequate protection against airborne viruses and bacteria.

Prototype sampling system for measuring workplace protection factors for gases and vapors

A prototype sampling system for measuring respirator workplace protection factors (WPFs) was developed. Methods for measuring the concentration of contaminants inside respirators have previously been described; however, these studies have typically involved continuous sampling of aerosols. Our work focuses on developing an intermittent sampling system designed to measure the concentration of gases and vapors during inspiration. This approach addresses two potential problems associated with continuous sampling: biased results due to lower contaminant concentrations and high humidity in exhaled air. The system consists of a pressure transducer circuit designed to activate a pair of personal sampling pumps during inspiration based on differential pressure inside the respirator. One pump draws air from inside the respirator while the second samples the ambient air. Solid granular adsorbent tubes are used to trap the contaminants, making the approach applicable to a large number of gases and vapors. Laboratory testing was performed using a respirator mounted on a headform connected to a breathing machine producing a sinusoidal flow pattern with an average flow rate of 20 L/min and a period of 3 seconds. The sampling system was adjusted to activate the pumps when the pressure inside the respirator was less than -0.1 inch H(2)O. Quantitative fit-tests using human subjects were conducted to evaluate the effect of the sampling system on respirator performance. A total of 299 fit-tests were completed for two different types of respirators (half- and full-facepiece) from two different manufacturers (MSA and North). Statistical tests showed no significant differences between mean fit factors for respirators equipped with the sampling system versus unmodified respirators. Field testing of the prototype sampling system was performed in livestock production facilities and estimates of WPFs for ammonia were obtained. Results demonstrate the feasibility of this approach and will be used in developing improved instrumentation for measuring WPFs.

Personal respiratory protection against Mycobacterium tuberculosis

Although there are no data demonstrating the effectiveness of personal respiratory protection in the prevention of occupational tuberculosis, there are sound theoretical bases supporting the use of respirators to reduce the risk of inhalational exposure. The major factor that limits the effectiveness of most respirators is the leakage between the face and the mask. There are data suggesting that traditional fit testing of respirators does not adequately predict the degree of protection in actual use, and more research is needed in that area. There is a large range of infectiousness of aerosols of TB, and classes of respirators vary greatly in the degree of protection they offer. I have argued that respirator selection should be based on anticipated exposures. High-risk exposures to TB are often associated with cough-inducing procedures or with aerosolization of infected tissues during autopsies. In my opinion, the most reasonable type of respirator for such high-risk situations in health care settings is a PAPR hood. The concentration of infectious aerosols in well-ventilated respiratory isolation rooms is likely to be very low, and the new N95 respirators offer a reasonable balance of comfort, cost, practicality, and protection. Preliminary data from mathematical modeling studies suggest there may be little additional benefit from more sophisticated personal respiratory protection in such settings. Additional research is needed to more accurately assess exposures to TB, to determine the size and aerodynamic behavior of TB generated by infectious patients, and to more accurately define the role and effectiveness of personal respiratory protection against TB.