N95 FFR Research Articles

The tiny effects of respiratory masks on physiological, subjective, and behavioral measures under mental load in a randomized controlled trial

Since the outbreak of the coronavirus disease (COVID-19), face coverings are recommended to diminish person-to-person transmission of the SARS-CoV-2 virus. Some public debates concern claims regarding risks caused by wearing face masks, like, e.g., decreased blood oxygen levels and impaired cognitive capabilities. The present, pre-registered study aims to contribute clarity by delivering a direct comparison of wearing an N95 respirator and wearing no face covering. We focused on a demanding situation to show that cognitive efficacy and individual states are equivalent in both conditions. We conducted a randomized-controlled crossover trial with 44 participants. Participants performed the task while wearing an N95 FFR versus wearing none. We measured physiological (blood oxygen saturation and heart rate variability), behavioral (parameters of performance in the task), and subjective (perceived mental load) data to substantiate our assumption as broadly as possible. We analyzed data regarding both statistical equivalence and differences. All of the investigated dimensions showed statistical equivalence given our pre-registered equivalence boundaries. None of the dimensions showed a significant difference between wearing an FFR and not wearing an FFR.Trial Registration: Preregistered with the Open Science Framework: https://osf.io/c2xp5 (15/11/2020). Retrospectively registered with German Clinical Trials Register: DRKS00024806 (18/03/2021).

Effect of N95 filtering facepiece respirators on dental health professionals with an emphasis on pulmonary function and heart rate: an intrasubject comparison

Despite the ubiquitous use of N95 filtering facepiece respirators (N95 FFR), published literature on the topic remains scarce, especially in relation to dental professionals. This study assesses the impact of N95 FFRs on blood oxygen saturation and heart rate of dental health professionals while performing procedures requiring varying degrees of physical exertion in an aerosol-rich environment. A total of 51 participants, consisting of 43 men and eight women aged between 23 and 31 years were recruited into the study. All subjects were well-versed in wearing personal protective equipment (PPE). A clinical grade pulse oximeter was used with a clamp placed around the fingertip or the earlobe of the participant. The selection of N95 FFR was based on fit and leakage. All data were collected once from the same participants using a surgical mask as a control. Data were collected again from the same subjects after 1, 2, and 3 hours of use. There were significant differences in both oxygen saturation (SpO2) and heart rate between the two groups after 1, 2, and 3 hours of wearing the respective masks. In healthy young individuals, wearing an N95 FFR for an extended period of time during clinical dental procedures reduced the SpO2level and increased the heart rate compared with a standard surgical mask. However, SpO2 levels remained within a healthy range of more than 95%, and heart rate was within acceptable limits.

Inactivation of Human Coronavirus by FATHHOME's Dry Sanitizer Device: Rapid and Eco-Friendly Ozone-Based Disinfection of SARS-CoV-2.

The pandemic of SARS-CoV-2/COVID-19 was reported in December 2019 in Wuhan, China. Pertaining to its high transmissibility and wide host adaptability, this unique human coronavirus spread across the planet inflicting 115 million people and causing 2.5 million deaths (as of March 3rd, 2021). Limited or negligible pre-existing immunity to multiple SARS-CoV-2 variants has resulted in severe morbidity and mortality worldwide, as well as a record-breaking surge in the use of medical-surgical supplies and personal protective equipment. In response to the global need for effective sterilization techniques, this study evaluated the virucidal efficacy of FATHHOME’s self-contained, ozone-based dry-sanitizing device, by dose and time response assessment. We tested inactivation of human coronavirus, HCoV-OC43, a close genetic model of SARS-CoV-2, on porous (N95 filtering facepiece respirator/FFR) and nonporous (glass) surfaces. We started our assays with 20 ppm-10 min ozone exposure, and effectively reduced 99.8% and 99.9% of virus from glass and N95 FFR surfaces, respectively. Importantly, the virus was completely inactivated, below the detection limit (over 6-log10 reduction) with 25 ppm-15 min ozone exposure on both tested surfaces. As expected, a higher ozone exposure (50 ppm-10 min) resulted in faster inactivation of HCoV-OC43 with 100% inactivation from both the surfaces, with no residual ozone present after completion of the 5-min post exposure recapture cycle and no measurable increase in ambient ozone levels. These results confirmed that FATHHOME’s device is suitable for rapid decontamination of SARS-CoV-2- from worn items, frequently touched items, and PPE including N95 FFRs, face shields, and other personal items.

Is N95 face mask linked to dizziness and headache?

ObjectivesDuring the COVID-19 pandemic, healthcare professionals are recommended to use PPE to prevent the transmission of disease. Healthcare workers who use N95 FFR, which has an important place, experience complaints such as headache and dizziness. In this study, we plan to find the cause of these complaints and aim to clarify whether they are associated with the use of N95 mask.MethodHealthcare workers first put on a surgical mask for at least 1 h and a maximum of 4 h, this process was then repeated on another day with the same workers wearing N95 masks. After removing the mask, capillary blood gases were taken and a questionnaire was given.ResultsThirty-four participants over the age of 18 were included in the study; 19 participants were female (56%) and 15 male (44%). The results of the capillary blood gas analysis after the use of surgical mask and N95 mask, respectively: pH: 7.43 ± 0.03; 7.48 ± 0.04 (p < 0.001); pCO2: 37.33 ± 8.81; 28.46 ± 7.77 mmHg (p < 0.001); HCO3: 24.92 ± 2.86; 23.73 ± 3.29 mmol/L (p = 0.131); Base excess (BE): 1.40 (− 3.90–3.10); − 2.68 (− 4.50–1.20) [median (Q1−Q3)] (p = 0.039); lactate: 1.74 ± 0.68; 1.91 ± 0.61 (p = 0314). Headache, attention deficit and difficulty in concentrating were significantly higher after using N95 mask.ConclusionRespiratory alkalosis and hypocarbia were detected after the use of N95. Acute respiratory alkalosis can cause headache, anxiety, tremor, muscle cramps. In this study, it was quantitatively shown that the participants’ symptoms were due to respiratory alkalosis and hypocarbia.

Comparison of Fit for Sealed and Loose-Fitting Surgical Masks and N95 Filtering Facepiece Respirators.

ObjectivesN95 filtering facepiece respirators (N95 FFRs) and surgical masks are comprised of multiple layers of nonwoven polypropylene. Tight-fitting N95 FFRs are respiratory protective devices (RPDs) designed to efficiently filter aerosols. During the COVID-19 pandemic, health care workers (HCWs) throughout the world continue to face shortages of disposable N95 FFRs. Existing version of widely available FDA cleared loose-fitting surgical masks with straps do not provide reliable protection against aerosols. We tested the faceseal of a modified strapless form-fitting sealed version of surgical mask using quantitative fit testing (QNFT) and compared the performance of this mask with that of N95 FFRs and unmodified loose-fitting surgical masks. MethodsTwenty HCWs participated in the study (10 women; 10 men; age 23–59 years). To create the sealed surgical masks, we removed the straps from loose-fitting surgical masks, made new folds, and used adhesive medical tape to secure the new design. All participants underwent QNFT with a loose-fitting surgical mask, the sealed surgical mask, and an N95 FFR; fit factors were recorded. Each QNFT was performed using a protocol of four exercises: (i) bending over, (ii) talking, (iii) moving head side to side, and (iv) moving head up and down. When the overall fit factor for the sealed surgical mask or N95 FFR was <100, the participant retook the test. Participants scored the breathability and comfort of the sealed surgical mask and N95 FFR on a visual analog scale (VAS) ranging from 0 (unfavorable) to 10 (favorable).ResultsThe median fit factor for the sealed surgical mask (53.8) was significantly higher than that of the loose-fitting surgical mask (3.0) but lower than that of the N95 FFR (177.0) (P < 0.001), equating to significantly lower inward leakage of ambient aerosols (measuring 0.04–0.06 µm) with the sealed surgical mask (geometric mean 1.79%; geometric standard deviation 1.45%; range 0.97–4.03%) than with the loose-fitting surgical mask (29.5%; 2.01%; 25–100.0%) but still higher than with the N95 FFR (0.66%; 1.46%; 0.50–1.97%) (P < 0.001). Sealed surgical masks led to a marked reduction (range 60–98%) in inward leakage of aerosols in all the participants, compared to loose-fitting surgical masks. Among the exercises, talking had a greater effect on reducing overall fit factor for the sealed surgical mask than for the N95 FFR; when talking was excluded, the fit factor for the sealed surgical mask improved significantly (median 53.8 to 81.5; P < 0.001). The sealed surgical mask, when compared with the N95 FFR, offered better reported breathability (median VAS 9 versus 5; P < 0.001) and comfort (9 versus 5; P < 0.001).ConclusionsWidely available loose-fitting surgical masks can be easily modified to achieve faceseal with adhesives. Unlike loose-fitting surgical masks, sealed surgical masks can markedly reduce inward leakage of aerosols and may therefore offer useful levels of respiratory protection during an extreme shortage of N95 FFRs and could benefit HCWs who cannot comply with N95 FFRs due to intolerance. However, because a wide range of surgical masks is commercially available, individual evaluation of such masks is highly recommended before sealed versions are used as RPDs.

Effects of volume, velocity, and composition on the resistance to synthetic blood penetration of N95 filtering facepiece respirators and other head/facial personal protective equipment

Surgical N95 filtering facepiece respirators (surgical N95 FFRs) are National Institute for Occupational Safety and Health-approved N95 filtering facepiece respirators (N95 FFRs) cleared by the Food and Drug Administration for resistance to liquid penetration and flammability. A recent study showed that several N95 FFR models performed as well as surgical N95 FFRs in synthetic blood penetration tests that evaluate resistance to penetration by horizontal projection. This aspect, in addition to the influence of other factors on liquid penetration, are not well studied. To address this issue, the effect of liquid volume (1 mL and 2 mL), spray velocity (450 cm/sec and 635 cm/sec), and liquid composition (synthetic blood and diluted synthetic blood) were evaluated. Four types of common protective devices were studied: N95 FFRs, surgical N95 FFRs, surgical masks, and powered air-purifying respirator (PAPR) hoods. For each protective device type, five models were analyzed using a protocol based on the F1862 ASTM International (2017) test method. Reduced liquid volume had a significant effect in only 3 of 20 models. Increased velocity had significantly greater penetration in 9 of 20 models. Diluted synthetic blood had significantly more penetration in 8 of 20 models. This last result was not expected because, in hydrostatic tests, surface tension of the diluted blood would be expected to reduce penetrability; however, across all models tested, data showed that the diluted spray was more penetrable. The study results suggest that fluid composition may be as important as velocity when considering liquid spray penetration. Furthermore, the penetrability of a spray may be inversely related to the penetrability through direct hydrostatic contact.

A low cost ingenious approach for ultraviolet decontamination of N95 filtering face-piece respirators to deal with dwindling supply during the COVID-19 pandemic

Introduction: COVID-19 pandemic caused by severe acute respiratory syndrome coronavirus-2 is rapidly evolving and hospitals are facing the issue of shortage of personal protective equipment (PPE) due to stringent requirements of PPE use. For reuse of N95 filtering face-piece respirators (N95FFR), we prepared an ingenious cabinet with ultraviolet light C (UV-C) using scarce material available during the lockdown period. Materials and Methods: Since like many other microbiology laboratories in medical colleges, we did not have access to viruses, we could not test our product with them. We thus tested the efficacy of the cabinet to decontaminate material using 0.5 McFarland standard broth of Escherichia coli 25922. The broth was exposed to UV-C inside the cabinet for 15 and 30 minutes in Petri dishes, with and without lids. The broth was subcultured on nutrient agar plates, both pre and post exposure. We also could not test integrity and static charge of the respirators; we relied on CDC data on the same. Results: It was observed that there was at least 4 log reduction (99.99%) in the number of viable E. coli on exposure to UV-C for 15 as well as 30 minutes. The plates with glass lids on did not show any reduction in number of viable bacilli. The reduction in number of E. coli was taken as surrogate marker for the reduction of ssRNA viruses. Conclusions: UV-C inside an ingeniously made cabinet can be used to decontaminate N95 FFR in exceptional circumstances of reduced supply under lockdown conditions of a pandemic.

Customized design and 3D printing of face seal for an N95 filtering facepiece respirator

ABSTRACTFiltering Facepiece Respirator (FFR) is the most common respirator users in the health care environment utilize for personal protection from outside particles. Comfort and fit are important while wearing an FFR. This paper proposes a novel technology to produce customized face seal design for improving the wearing comfort and fit of FFR wearers. In order to customize the design of face seals, we scanned the faces of three subjects using three-dimensional (3D) laser scanning method. A customized face seal for a 3M 8210 N95 FFR for each headform was designed using reverse engineering technique. Next, the face seal prototypes were fabricated with Acrylonitrile Butadiene Styrene (ABS) plastic using the 3D printing method. A force sensing system based on Arduino Uno R3 was developed, and the force sensor of this system was inserted between the FFR and headform to measure contact pressure. Experimental results showed that the newly designed FFR face seal provided the subjects with an improved contact pressure.

Powered air-purifying respirator use in healthcare: Effects on thermal sensations and comfort

ABSTRACTTwelve subjects wore an N95 filtering facepiece respirator (N95 FFR), one tight-fitting full facepiece powered air-purifying respirator (PAPR), two loose-fitting PAPRs, and one elastomeric/PAPR hybrid for 1 hr each during treadmill walking at 5.6 km/hr while undergoing physiological and subjective response monitoring. No significant interaction (p ≥ .05) was noted between the five respirators in heart rate, respiratory rate, oxygen saturation, transcutaneous carbon dioxide, and perceptions of breathing effort or discomfort, exertion, facial heat, and overall body heat. Respirator deadspace heat/humidity were significantly greater for the N95 FFR, whereas tympanic forehead skin temperatures were significantly greater for the hybrid PAPR. Temperature of the facial skin covered by the respirator was equivalent for the N95 FFR and hybrid PAPR, and both were significantly higher than for the other three PAPRs. Perception of eye dryness was significantly greater for a tight-fitting full facepiece PAPR than the N95 FFR and hybrid PAPR. At a low-moderate work rate over 1 hr, effects on cardiopulmonary variables, breathing perceptions, and facial and overall body heat perceptions did not differ significantly between the four PAPRs and a N95 FFR, but the tight-fitting, full facepiece PAPR increased perceptions of eye dryness. The two loose-fitting PAPRs and the full facepiece tight-fitting PAPR ameliorated exercise-induced increases in facial temperature, but this did not translate to improved perception of facial heat and overall body heat.

A comparison of facemask and respirator filtration test methods

ABSTRACTNIOSH published a Federal Register Notice to explore the possibility of incorporating FDA required filtration tests for surgical masks (SMs) in the 42 CFR Part 84 respirator certification process. There have been no published studies comparing the filtration efficiency test methods used for NIOSH certification of N95 filtering facepiece respirators (N95 FFRs) with those used by the FDA for clearance of SMs. To address this issue, filtration efficiencies of “N95 FFRs” including six N95 FFR models and three surgical N95 FFR models, and three SM models were measured using the NIOSH NaCl aerosol test method, and FDA required particulate filtration efficiency (PFE) and bacterial filtration efficiency (BFE) methods, and viral filtration efficiency (VFE) method. Five samples of each model were tested using each method. Both PFE and BFE tests were done using unneutralized particles as per FDA guidance document. PFE was measured using 0.1 µm size polystyrene latex particles and BFE with ∼3.0 µm size particles containing Staphylococcus aureus bacteria. VFE was obtained using ∼3.0 µm size particles containing phiX 174 as the challenge virus and Escherichia coli as the host. Results showed that the efficiencies measured by the NIOSH NaCl method for “N95 FFRs” were from 98.15–99.68% compared to 99.74–99.99% for PFE, 99.62–99.9% for BFE, and 99.8–99.9% for VFE methods. Efficiencies by the NIOSH NaCl method were significantly (p = <0.05) lower than the other methods. SMs showed lower efficiencies (54.72–88.40%) than “N95 FFRs” measured by the NIOSH NaCl method, while PFE, BFE, and VFE methods produced no significant difference. The above results show that the NIOSH NaCl method is relatively conservative and is able to identify poorly performing filtration devices. The higher efficiencies obtained using PFE, BFE and VFE methods show that adding these supplemental particle penetration methods will not improve respirator certification.

Speech intelligibility assessment of protective facemasks and air-purifying respirators

ABSTRACTSpeech Intelligibility (SI) is the perceived quality of sound transmission. In healthcare settings, the ability to communicate clearly with coworkers, patients, etc., is crucial to quality patient care and safety. The objectives of this study were to: (1) assess the suitability of the Speech Transmission Index (STI) methods for testing reusable and disposable facial and respiratory personal protective equipment (protective facemasks [PF], N95 filtering facepiece respirators [N95 FFR], and elastomeric half-mask air-purifying respirators [EAPR]) commonly worn by healthcare workers; (2) quantify STI levels of these devices; and (3) contribute to the scientific body of knowledge in the area of SI. SI was assessed using the STI under two experimental conditions: (1) a modified version of the National Fire Protection Association 1981 Supplementary Voice Communications System Performance Test at a Signal to Noise Ratio (SNR) of −15 (66 dBA) and (2) STI measurements utilizing a range of modified pink noise levels (52.5 dBA (−2 SNR) – 72.5 dBA (+7 SNR)) in 5.0 dBA increments. The PF models (Kimberly Clark 49214 and 3 M 1818) had the least effect on SI interference, typically deviating from the STI baseline (no-mask condition) by 3% and 4% STI, respectively. The N95FFR (3 M 1870, 3 M 1860) had more effect on SI interference, typically differing from baseline by 13% and 17%, respectively, for models tested. The EAPR models (Scott Xcel and North 5500) had the most significant impact on SI, differing from baseline by 42% for models tested. This data offers insight into the performance of these apparatus with respect to STI and may serve as a reference point for future respirator design considerations, standards development, testing and certification activities.

Physiological and subjective responses to breathing resistance of N95 filtering facepiece respirators in still-sitting and walking

The objective of this study was to assess the impact of breathing resistance on physiological and subjective responses to N95 filtering facepiece respirators (N95 FFRs) during still-sitting and walking. Fifteen subjects sat for 5 min and walked for 5 min while wearing 2 different models of N95 FFRs, 1 model of which was equipped with exhalation valves (N95 FFR/EV). The subjects were monitored by a modified monitoring garment for respiratory signals (RSP) and surface electromyography (sEMG). Subjects also were asked to complete subjective ratings of overall breathing resistance. The results of the physiological measurements in this study have shown that compared with no respirator, wearing N95 FFR had a direct effect on increasing respiratory amplitude, muscle activity and fatigue of abdominal, and fatigue of scalene; The use of N95 FFR/EV conferred limited physiological benefit over N95 FFR in walking; Compared with sitting still, walking significantly decreased respiratory amplitude, but increased respiratory rate, the muscle activity of sternomastoid, scalene, diaphragm and abdominal, the fatigue of scalene and intercostal. The subjective survey showed that wearing respirators and walking had a direct effect on improving the subjective overall breathing resistance. Significantly low to moderate correlation coefficients were shown between physiological values (respiratory amplitude, the muscle activity of diaphragm, the muscle activity and fatigue of scalene and abdominal), and the subjective breathing resistance. This is the first reported study that combines RSP, sEMG and subjective overall breathing resistance to evaluate breathing resistance on the use of N95 FFR in sitting still and walking. The physiological responses to breathing resistance of wearing a N95 FFR for 5 min in still-sitting and walking are relatively small and should generally be well tolerated by healthy persons. Relevance to industryThis paper's findings can be readily employed by respirator manufactures and administrations for evaluating the respiratory muscle function (activity, fatigue) and breathing parameters of wearing N95 FFRs. Observations of present study are in support of issuing new regulations to raise the limit for breathing resistance over short periods at low-moderate exertion tasks. Thus, the manufacturers could easily fulfill the requirements for collection efficiency by adding more filter media while still meeting the requirements for air resistance.

Physiologic and fit factor profiles of N95 and P100 filtering facepiece respirators for use in hot, humid environments

BackgroundTo determine if hot, humid ambient conditions impact filtering facepiece respirators' (FFRs') fit, and to evaluate differences in physiologic and subjective responses between N95 FFRs and P100 FFRs.MethodsTwelve subjects had physiologic monitoring and subjective perceptions monitored over 1 hour of treadmill exercise (5.6 km/h) in an environmental chamber (35°C, relative humidity 50%) wearing an N95 FFR, P100 FFR, or no respirator. Respirator quantitative fit testing was done before and after exercise.ResultsThere was no significant difference in pass rates for both FFRs on initial fit testing, but subjects who passed were more likely to fail the postexercise test with N95 FFRs (P = .01). Wearing FFRs increased the temperature of facial skin covered by the FFR (P = .009) and breathing discomfort (P = .002). No significant differences were noted in other measured variables (heart rate, respiratory rate, oxygen saturation, transcutaneous carbon dioxide level, rectal temperature, global skin temperature, core temperature, and subjective perceptions) between controls and FFRs and between FFR models.ConclusionAfter 1 hour of exercise in hot, humid ambient conditions, P100 FFRs retained better fit than N95 FFRs, without additional physiologic or subjective impact. Wearing FFRs under these conditions does not add to the body's thermophysiologic or perceptual burdens.

Effect of Pregnancy Upon Facial Anthropometrics and Respirator Fit Testing

Workers required to wear respirators must undergo additional respirator fit testing if a significant change in body weight occurs. Approximately 10% of working women of reproductive age will be pregnant and experience a significant change in weight, yet the effect of pregnancy-associated weight gain on respirator fit is unknown. Cephalo-facial anthropometric measurements and quantitative fit testing of N95 filtering facepiece respirators (N95 FFR) of 15 pregnant women and 15 matched, non-pregnant women were undertaken for comparisons between the groups. There were no significant differences between pregnant and non-pregnant women with respect to cephalo-facial anthropometric measurements or N95 FFR quantitative fit tests. Healthy pregnant workers, who adhere to the recommended weight gain limits of pregnancy, are unlikely to experience an increase in cephalo-facial dimensions that would mandate additional N95 FFR fit testing above that which is normally required on an annual basis.

Potential Role of Infrared Imaging for Detecting Facial Seal Leaks in Filtering Facepiece Respirator Users

Infrared imaging (IRI) can detect airflow through and near respirator masks based upon temperature differences between ambient and exhaled air. This study investigated the potential usefulness of IRI for detecting leaks and providing insight into the sites and significance of leaks. Subjects (n = 165) used filtering facepiece N95 respirators (N95 FFR) in the course of a research study concerning training modalities. Short sequence video infrared images were obtained during use and with intentionally introduced facial seal leaks. Fit factor (FF) was measured with condensation nuclei count methods. IRI detected leaks were scored on a four-point scale and summarized as the Total Leak Score (TLS) over six coding regions and the presence or absence of a “Big Leak” (BL) in any location. A semi-automated interpretation algorithm was also developed. IRI detected leaks are particularly common in the nasal region, but these are of limited significance. IR imaging could effectively identify many large leaks. The TLS was related to FF. Although IRI scores were related to FF, the relationship is insufficiently close for IRI to substitute for quantitative fit-testing. Using FFRs infrared techniques have potential for identifying situations with very inadequate respiratory protection.

Effect of wearing an N95 respirator on infrared tympanic membrane temperature measurements.

To determine the impact of wearing an N95 filtering facepiece respirator (N95 FFR) on tympanic temperature measurements. TMT measurements, with and without wearing an N95 filtering facepiece respirator (N95 FFR) were obtained at the onset and termination of 1h of treadmill exercise in 21 subjects, and at staggered time intervals (0, 20, 40, 60min) during combined sedentary activity and exercise of another 46 subjects, to determine any effect on TMT. A total of 877 TMT measurements were obtained that demonstrated a mean TMT increase of 0.05°C in the first study group (p=0.04) and a 0.19°C decrease in the second study group (p<0.001) with the wearing of an N95 FFR, both of which were lower than controls. Wearing an N95 FFR for 1h, at different levels of activity, results in significantly lower TMT values than not wearing an N95 FFR, but the magnitude of the changes would likely have minimal clinical significance.

Evaluation of Minnesota and Illinois Hospital Respiratory Protection Programs and Health Care Worker Respirator Use

The objective of this study was to assess respiratory protection programs for aerosol-transmissible diseases in acute care hospitals for conformance with regulatory requirements and public health guidelines. Twenty-eight representative hospitals were selected by size, location, and ownership in Minnesota and Illinois. Interviews were conducted with 363 health care workers and 171 managers from high-risk departments. Written programs from each hospital were reviewed for required elements. Seventy-seven health care workers were observed donning and doffing a FFR. The most serious deficiency in many written programs was failure to identify a program administrator. Most written programs lacked adequate details about medical evaluation, fit-testing, and training and did not include a comprehensive risk assessment for aerosol transmissible diseases; tuberculosis was often the only pathogen addressed. Employees with the highest probability of tuberculosis exposure were most likely to pick a respirator for close contact, but higher levels of respiratory protection were rarely selected for aerosol-generating procedures. Surgical masks were most commonly selected for close contact with droplet disease- or influenza-infected patients; better protection (e.g., respirator) was rarely selected for higher-risk exposures. Most of the observed health care workers had access to a NIOSH-certified N95 FFR, properly positioned the facepiece, and formed the nose clip. The most frequent deficiencies were failure to correctly place straps, perform a user seal check, and remove the respirator using straps.

N95 respirator use during advanced pregnancy

To determine the physiological and subjective effects of wearing an N95 filtering facepiece respirator (N95 FFR) in advanced stages of pregnancy. Healthy pregnant women (n = 22) and nonpregnant women (n = 22) had physiological and subjective measurements taken with and without wearing an N95 FFR during exercise and postural sedentary activities over a 1-hour period. There were no differences between the pregnant and nonpregnant women with respect to heart rate, respiratory rate, oxygen saturation, transcutaneous carbon dioxide level, chest wall temperature, aural temperature, and subjective perceptions of exertion and thermal comfort. No significant effect on fetal heart rate was noted. Healthy pregnant women wearing an N95 FFR for 1 hour during exercise and sedentary activities did not exhibit any significant differences in measured physiological and subjective responses compared with nonpregnant women.

Flat Fold and Cup-Shaped N95 Filtering Facepiece Respirator Face Seal Area and Pressure Determinations: A Stereophotogrammetry Study

Twenty subjects underwent quantitative respirator fit testing with two styles (flat fold, cup-shaped) of N95 filtering facepiece respirators (N95 FFRs). Passing a fit test was followed by stereophotogrammetry to determine the face seal area and computation of seal pressure. There were significantly different seal pressures (p < 0.01) between standard size flat fold and cup-shaped N95 FFRs but no significant differences in face seal area. No significant differences were noted in fit factors, but more individuals passed fit testing wearing flat fold respirators. The ability of flat fold N95 FFRs, at lower seal pressures, to obtain similar fit factors as cup-shaped N95 FFR at higher seal pressures offers the possibility of enhanced facial comfort without a loss of protection. Stereophotogrammetry offers a relatively simple, non-invasive technology to evaluate various properties of N95 FFR fit.

Analysis of Forces Generated by N95 Filtering Facepiece Respirator Tethering Devices: A Pilot Study

The restorative forces of elasticized tethering devices on N95 filtering facepiece respirators (N95 FFR), that occur in response to the application of a load (applied force) during donning, create the requisite pressure to effectively seal the respirator against the face and prevent excessive inward migration of harmful elements. Many workers don and doff the same N95 FFR multiple times in the course of a single workday, yet little is known regarding the possible degradation of these restorative loads and, by implication, protection with multiple donnings. This laboratory pilot study evaluated the degradation in loads of tethering devices of three models of N95 FFRs subjected to the strain of five wear periods of 15 min interspersed with 15-min periods without wear. Data indicate that there were load degradations at each donning that differed significantly with the FFR model (p = <0.001), the greatest of which occurred with the first donning. The N95 FFR model with the lowest restorative loads was able to pass fit testing in a previous study, indicating that lower loads, perhaps coupled with FFR model-specific features, are sufficient to provide an adequate face/FFR interface seal. Tethering devices are importantly related to issues of comfort and protection afforded by N95 FFR and additional research is warranted.