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ISSN: 2637-6679

Research and Reviews on Healthcare: Open Access Journal

Review Article(ISSN: 2637-6679)

Efficiency and Burdens of Wearing Masks for Protection Against Sars-Cov-2: A Narrative Review Focused on the Current Situation at Workplaces Volume 7 - Issue 4

Jürgen Bünger*, Eike Maximilian Marek, Vera van Kampen and Thomas Brüning

  • Institute for Prevention and Occupational Medicine of the German Social Accident Insurance - Institute of the Ruhr-University Bochum (IPA), Bochum, Germany

Received: March 11, 2022;   Published: March 18, 2022

Corresponding author: Jürgen Bünger, Institute for Prevention and Occupational Medicine of the German Social Accident Insurance - Institute of the Ruhr-University Bochum (IPA), Bürkle-de-la-Camp-Platz 1, 44789 Bochum, Germany

DOI: 10.32474/RRHOAJ.2022.07.000266

Abstract PDF


At workplaces, many additional conditions and influences must be considered when choosing adequate personal protection equipment, including masks to protect from SARS-CoV-2 infection and transmission to other workmates. Conditions like type, proximity and duration of contact with colleagues, duration of mask wear, virus load, heat, humidity must be included for the risk analysis and decision if a mask is needed and if yes, what kind of mask is the best choice. A good scientific knowledge on the efficiency and burden of protection against SARS-CoV-2 by wearing masks is useful as an additional fundamental prerequisite for this decision. Depending on the type of mask, respiratory masks can be effective for both self-protection and protection of others (Asadi et al. [1], Chu et al. [2], Leung et al. [3], Liang et al. [4]). Jefferson and colleagues presented the state of knowledge on the effectiveness of masks in preventing the transmission of respiratory viruses until 2020 in a comprehensive literature review. The knowledge gained in the meantime (01.01.2022) will be briefly supplemented here. However, the main concern of this overview is the evaluation of the current scientific data on possible objective and subjective strains and stresses caused by wearing masks at rest and under different working (exercising) conditions.

Efficiency of protective masks

At workplaces, many additional conditions and influences must be considered when choosing adequate personal protection equipment, including masks to protect from SARS-CoV-2 infection and transmission to other workmates. Conditions like type, proximity and duration of contact with colleagues, duration of mask wear, virus load, heat, humidity must be included for the risk analysis and decision if a mask is needed and if yes, what kind of mask is the best choice. A good scientific knowledge on the efficiency and burden of protection against SARS-CoV-2 by wearing masks is useful as an additional fundamental prerequisite for this decision. Depending on the type of mask, respiratory masks can be effective for both self-protection and protection of others (Asadi et al. [1], Chu et al. [2], Leung et al. [3], Liang et al. [4]). Jefferson and colleagues presented the state of knowledge on the effectiveness of masks in preventing the transmission of respiratory viruses until 2020 in a comprehensive literature review. The knowledge gained in the meantime (01.01.2022) will be briefly supplemented here. However, the main concern of this overview is the evaluation of the current scientific data on possible objective and subjective strains and stresses caused by wearing masks at rest and under different working (exercising) conditions.

Efficiency of protective masks

In a Cochrane review that was updated several times (2007 - 2020), the effectiveness of protective masks in reducing the transmission of viruses was still classified as uncertain. The pooled results of randomized clinical trials (RCTs) showed no clear reduction in respiratory viral infections (mainly influenza) with the use of medical/surgical masks or FFP2/N95 masks (Jefferson et al. [5]). However, no studies on protection against SARS-CoV-2 were included in this research. In the meantime, numerous other experimental, clinical, and population-based studies have been published that show good efficiency, especially of FFP2/N95 masks, but also of surgical masks (SM) and to a lesser extent of community masks (CM) in protecting against SARS-CoV-2. The good effectiveness of masks against the transmission of SARS-CoV-2 or COVID-19 was already evident at the beginning of the pandemic through lower infection rates of healthcare workers despite the much higher exposure to SARS-CoV-2 compared to the infection rates of the population in New York and Long Island (Jeremias et al. [6]). After the introduction of the mask requirement in German cities and communities, the number of cases fell rapidly. For example, the 7-day incidence fell to zero within 2 weeks in the city of Jena (Mitze et al. [7]). A study in 15 states of the USA and Washington, DC (Lyu et al. [8]) and a nationwide study in Canada (Karaivanov et al. [9]) showed comparable results. The reduction of SARS-CoV-2 transmission by wearing masks has also been convincingly demonstrated in airplanes (Freedman & Wilder-Smith [10], Doung Ngern et al. [11]). In a comprehensive review with meta-analyses, Chu and co-authors (2020) concluded that face mask use could lead to a significant reduction in the risk of infection. The effectiveness of FFP2/N95 masks was rated higher than that of SM or CM (Chu et al. [2]). In the meantime, other reviews (Ju et al. [12], Li et al. 2021, Tran et al. [13], Zhang et al. [14]) have also been published that support the protection against COVID-19 infection by wearing masks. Ju et al. [15] conclude that while definitive evidence is still lacking for the superiority of N95 masks compared to SM for protection against COVID-19, experimental laboratory tests are conclusive and consistent in establishing the superior performance of FFP2/N95 versus SM.

In these experimental studies, the protection afforded by wearing masks was examined and was convincingly demonstrated, especially for FFP2 and SM (Bagheri et al. [16], Cheng et al. [17], Sickbert Bennett et al. [18], Ueki et al. [19]). Results for CM were less convincing (Maurer et al. [20]). Bagheri and colleagues (2021) used a comprehensive database with information on particle size distribution in the airways, the physics of the exhalation flow, mask leakage, and further parameters for the multimodal calculation of the risk of exposure and infection when wearing face masks under various environmental conditions. For a typical SARS-CoV-2 viral load, these authors calculated a transmission probability of less than 30% for 2 people both wearing SM at a distance of 1.5 m after 1 hour. If both wear a well-fitting FFP2, the risk is only 0.4%. The authors conclude that wearing appropriate masks provides excellent protection for others and oneself (Bagheri et al. [16]). In a similarly designed study (Cheng et al. [17]), the authors conclude that SM can effectively prevented the spread of SARS-CoV-2 in the case of contact under conditions of low virus density. In potentially virus-rich indoor environments, including medical institutions and hospitals, FFP2 or FFP3 masks and other protective equipment are required. Sickbert Bennett et al. [18] evaluated 29 different N95 masks and found that compliant products offer very good protection and that re-sterilized N95 respirators can also be used. Ueki et al. [19] found that CM, SM, and N95 have a protective effect in relation to the transmission of infectious droplets and aerosols of SARS-CoV-2. The protection provided by SM and N95 masks is better than by CM. However, all 3 types of masks could not completely prevent the transmission of virus droplets or aerosols, even with a good fit. Maurer et al. [20] investigated reusable CM and measured a filtration efficiency ranging from 34.9% ± 1.25% to 88.7% ± 1.18%. The respiratory resistance ranged from 4.3 ± 0.06 Pa/cm2to 122.4 ± 0.12 Pa/cm2. A high correlation was found between filtration efficiency and breathing resistance (R2 = 0.88). In a study by Dreller et al. [21], various SM and FFP were examined based on the EN 149 standard. With an air flow rate of 95 L/min, the breathing resistance fell into the range of 10 - 280 Pa (corresponding to 0.1 - 2.8 mbar), which is in the range of the masks used in current mask studies. These Data were confirmed by Marek and coworkers in 2022 [22].

Objective and subjective physical loads and strains


Hopkins et al. [23] reviewed the literature on the effects of different face masks and respirators on the airways during physical activity. Overall, according to the authors, the available data suggest that the effects on work of breathing, blood gases and other physiological parameters during physical activity are small. There is currently no evidence of gender or age-related differences in physiological responses to training while wearing a mask. A systematic review and meta-analysis were carried out by Shaw and co-authors [24] on the effects of wearing masks (CM, SM, FFP2/N95) during physical exertion (training). Twenty-two studies with 1,573 participants (620 women, 953 men) were included. SM or N95 had no effect on exercise performance (SMD 0.05 [0.16, 0.07] and SMD 0.16 [0.54, 0.22], respectively). However, there was an increased subjectively perceived exertion for SM (SMD 0.33 [0.09, 0.58]) and FFP2/N95 (SMD 0.61 [0.23, 0.99]) and for dyspnea (SMD 0.6 [0.3, 0.9]) for all masks. End-tidal CO2 was slightly increased for SM (MD 3.3 mmHg [1.0, 5.6]) and for FFP2/ N95 (MD 3.7 mmHg [3.0, 4.4]), as well as heart rate (HR) in FFP2/N95 (SMD 2.01 [0.13, 3.89] beats/min). According to the authors, face masks can be used during physical exertion without affecting performance and with minimal impact on physiological variables (Shaw et al. [24]). Engeroff et al. [25] included 14 RCTs with 246 study participants for their review and found general changes when wearing masks. Mask wearing lead to a decrease in oxygen saturation (SO2) during intensive training (SMD −0.40 [95% CI:−0.70, −0.09]), mostly attributed to FFP2/N95.

Wearing a mask at rest

Engeroff [25] found the following changes when wearing infection protection masks at rest: The use of masks changes the breathing rate and depth of breathing. FFP2 or N95 respirator masks and SM tended to lead to an increase in SO2 at rest. Compared to SM, FFP2 and N95 had a stronger impact on gas exchange (Engeroff et al. [25]). Lässing et al. [26] examined the changes in lung function when wearing a SM at rest. Respiratory resistance was almost twice as high with SM than without mask (MNS: 0.58 ± 0.16 kPa/L; control: 0.32 ± 0.08 kPa/L; p < 0.01). Mapelli et al. [27] showed a reduction in static and dynamic lung function parameters (FEV1, CO2, etc.....) when wearing SM or N95.

Wearing a mask under physical stress

Short term maximum physical stress

The changes in lung function and gas exchange associated with using masks at rest differ from the effects of wearing masks during physical activity. Mask use during strenuous activities shows the greatest impact on oxygen uptake (Engeroff et al. [25]). Cardiopulmonary stress from wearing masks has been observed in numerous studies in which the strain on the subjects was stepwise increased up to the maximum load [28-44]. In summary, a measurable but non-health-relevant drop in oxygen partial pressure (PO2) was observed in these studies. Slight increases in the carbon dioxide partial pressure (PCO2) were also measured in addition but were assessed as not relevant to health. It should be noted that the sometimes very high loads of up to 280 watts carried out in the studies do not represent the typical conditions at workplaces. In addition, the measurements were predominantly carried out on young, welltrained people (thereof relatively few women). For these reasons, the mentioned studies were not further analysed in the context of this evaluation.

Typical workplace load/continuous load

Typical workplace stresses were more likely to be identified in the study by Georgi et al. [45] investigating 24 hospital employees (age 44.7 ± 11.7 years; 46 % male; BMI 25.4 ± 4.3 kg/m2; 26.9% smokers; 19.2 % hypertensive). These subjects were examined by means of ergometry at typical workplace loads (50/75/100 watts, for three minutes each in direct succession) without a mask and wearing CM, SM, or FFP2. In particular, less trained people (strong increase in HR) reported symptoms such as dyspnoea, headaches, feeling hot or dizzy with all mask types, but especially with FFP2, even at low levels of exertion. Overall, the authors found a “a measurable but clinically irrelevant effect on blood gases and vital parameters in people of working age with no known underlying cardiopulmonary disease”. Lässing et al. [26] investigated the physiological effects of SM at constant loads over 30 min on 14 healthy men (age 25.7 ± 3.5 years). Although the subjects exercised only at 66 % of the individual maximum load, this corresponded to a power of 200 watts, indicating a very welltrained test group. The loads with masks over 30 min resulted in significantly different respiratory minute volumes (SM: 77.1 ± 9.3L/min; control: 82.4 ± 10.7 L/min; p < 0.01), oxygen uptake (SM: 33.1 ± 5 mL/min/kg; control 34.5 ± 6 mL/min/kg; p = 0.04) and heart rates (SM: 160.1 ± 11.2 beats/min; control: 154.5 ± 11.4 bpm; p<0.01) compared to those without masks (controls). The authors conclude that SM increases respiratory resistance and heart rate during constant exercise in healthy volunteers. Perceived exertion and endurance performance did not differ significantly. Doherty et al. [46] determined the influence of wearing CM and SM on the cardiopulmonary functions of 12 persons (5 women) during moderately intensive ergometer training (70% of the maximum heart rate, or 74 - 107 watts) over a period of 5 minutes. There were no differences in breathing rate, heart rate, or SO2. The authors conclude that wearing a mask (CM/ SM) during short-term exercise with moderate-intensity results in minimal effects on cardiopulmonary stress in young, healthy individuals and may subjectively increase feelings of dyspnoea Doherty et al. [46].

Cabanillas Barea et al. [47] investigated in 50 healthy volunteers whether the use of masks (FFP2/N95, SM) compared to the situation without a mask causes effects in the 6-minute walk test (6MWT). Significant differences were observed between the three situations in terms of subjectively perceived dyspnoea (FFP2/N95 SM > no mask). No significant differences were found regarding the walking distances covered in the 6MWT, the heart rate, blood gases, and respiratory muscle tone (Cabanillas Barea et al. [46]). Shein et al. [48] investigated PCO2 and SO2 at the end of six 10-minute periods of sitting quietly and walking briskly without a mask, wearing CM or SM, respectively. There were no episodes of hypoxemia or hypercapnia among the 50 adult volunteers studied (mean age 33 years; 32 % with comorbidities). There were no statistically significant differences in PCO2 or SO2 between measurements without a mask and those while wearing either mask type, either at rest or after 10 minutes of brisk walking. The authors conclude that the risk of pathological gas exchange disorders in the general adult population when using cloth and surgical masks is close to zero (Shein et al. [48]). Reychler et al. [49] investigated the influence of CM and SM using a relatively rarely used stress test (standing up and sitting down on a chair for 1 min, corresponding to submaximal stress) on 20 young persons (9 women, 11 men, age 22±2 years) The authors conclude that in healthy adults, both CM and SM have minimal to no effect on dyspnoea, cardiorespiratory parameters, and exercise performance during a brief submaximal exercise test, with the observed effects being slightly more pronounced in CM.

Wearing masks for a longer period at work

In this literature search, 5 interventional or observational studies were identified in which the mask was worn for a period of 30 minutes or longer with simultaneous measurement of physiological parameters and survey of subjective stress. In the study by Butz [50], the accumulation of carbon dioxide (CO2) behind SM was examined over a period of 30 minutes. The accumulation led to increased rebreathing of CO2 and this in turn led to a significant increase in PCO2 in the tested subjects. The accumulation of CO2 under surgical masks in normally breathing people is caused by the impaired permeability of the mask (Butz [50]). In a study by Roberge et al. [51], 20 people (13 men, 7 women, all non-smokers) walked on a treadmill for 1 hour with and without SM at a walking speed of 5.6 km/h monitoring heart rate, respiratory rate, so2, transcutaneous CO2 as well as relative humidity and skin temperature under the mask. Rating scales were used for perceptions of exertion and warmth. Use of the SM resulted in increases in heart rate (9.5 bpm; p<0.001), respiratory rate (1.6 breaths/min; p=0.02), and transcutaneous carbon dioxide (2.17 mm Hg; p= 0.0006). The temperature rise of the skin covered by the mask was 1.76°C. The subjective perception of warmth was neutral to slightly hot. Perceived exposure ranged from very light to fairly light. Overall, the authors conclude that the use of the SM for 1 hour during light to moderate work is not associated with clinically significant physiological effects or a significant subjective perception of exertion or heat (Roberge et al. [51]). The study by Nwosu et al. [52] included 76 healthcare workers who wore different types of masks (CM, SM, N95) over a period of 68-480 minutes. The authors concluded that N95 may cause greater subjective discomfort than SM. Neither mask affected arterial oxygen saturation. Similar effects were shown in the earlier work by Shenal et al. [53] and Rebmann et al. [54], in which subjective complaints increased with increasing wearing time (8-12 hours), but the masks did not lead to any clinically relevant physiological stress on the nursing staff. In a review article, Gupta [54] defined the microclimate behind the mask primarily in terms of increased heat and moisture accumulation. He states that removing the face mask immediately neutralizes the increased temperature and relative humidity behind the mask. Therefore, taking off the mask for a short time under safe precautions at home/workplace/in a facility provides for a temporary “mask vacation”.

Cognitive function

Spang and Pieper [56] investigated the effects of wearing an N95 mask on demanding cognitive tasks for 15 minutes in 44 people (24 women, ages 18-65, academics, students). Parameters related to physiology (SO2, HR), behaviour (performance parameters in the tasks), and subjectively perceived mental stress were measured. All endpoints examined showed statistical equivalence within the specified limits. No parameters showed a significant difference between wearing the mask compared to the situation without mask. The authors interpret the data that there are no statistical differences between the two groups (Spang et al. [56]). Slimani et al. [57] studied the effect of a physical warm-up program with MNB/CM and no mask wearing on cognitive function in 17 healthy non-smoking sports students (8 females, age = 17.6 years). The warm-up improved cognitive skills. Results showed significant differences (p<0.001) between MNB/CM and control for concentration (186.06±15.47 vs. 178.12±13.66), total number of errors (23.47±14, 50 vs. 29.06±13.74) and subjective effort (6.0±1.37 vs. 4.7±0.85). Wearing MNB/CM had overall positive effects on cognitive abilities.


Self-protection against viral infections by wearing masks is very efficient according to experimental studies. Masks prevent transmission of viruses like SARS-CoV-2. Protection by FFP2/N95 is better than by SM. CM can protect to a lesser extent depending on the making of the masks (fit and material). It is difficult to show the effectiveness of wearing masks in clinical controlled trials due to extremely varying environmental and occupational conditions such as virus load, humidity, temperature, and so on. Wearing masks at workplaces is mandatory when secure social distancing is not possible and may last 8 hours and more . However, the increased breathing resistance of the mask materials leads to enhanced breathwork and wearing the mask causes additional physical strain and subjective discomfort depending on workload, climatic conditions, and duration. Therefore, risk assessment should be performed for each occupational task, if periods without wearing the mask are necessary. Short-term removing of the mask is adequate when the physical load is low and only the higher temperature and humidity must be considered. Breaks should be extended under higher physical workloads and unusual climatic conditions.


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