Prolonged mask use in safety-critical roles, and its potential impact on fatigue


By: Tim Smithies and Dr Ian Dunican

Disclaimer and information: This article does not aim to provide health advice or contravene any country’s local, state, or federal health advice. In addition, this article is not health advice for the general population. We have authored this article to summarise the latest scientific evidence and information based upon client and individual queries related to prolonged mask-wearing in safety-critical roles.

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The COVID-19 pandemic has brought with it substantial changes to our everyday life. From lockdowns to online work, vaccine passports, mandates and travel restrictions, the way we live our lives has been forced to change due to the virus and our governments’ measures to stop its spread.

One of the measures used by almost the entire world is some form of mandatory mask-wearing in specific environments. According to the Centre for Disease Control and Prevention (CDC), ‘Masking is a critical public health tool for preventing the spread of COVID-19’ (1). However, concerns have been raised that mask-wearing could result in decreased work capacity, increased fatigue, and even reduced cognitive and physical performance during physical work or in high-pressure environments (i.e., safety-critical workers). The primary worry is that mask-wearing could cause changes in gas exchange, specifically decreasing oxygen saturation and elevating CO2 intake. In addition, other concerns have been raised over respiratory fatigue due to increased breathing resistance, discomfort/pain from prolonged wearing, and behavioural changes such as reducing food and water intake (2-4).

Not all masks are made equal. Therefore, it is vital to consider the differences between mask types for the effectiveness of transmission reduction. It may also be essential to consider the difference in mask types for adverse effects on work capacity and fatigue. Reusable cloth masks or disposable procedure masks (also known as surgery masks) are the most used masks on a day-to-day basis. Respirators (such as the well-known N95 respirator, though there are many others) are also worn by some. Compared to the other masks above, they are purported to provide increased protection of COVID 19 transmission for yourself and others.

So firstly, do wearing these masks impact gas exchange, breathing resistance, performance/work capacity and perceived exertion?

When searching for an answer to this, we found multiple studies finding masks to have significant negative effects and masks to have no effect. Of course, this is commonplace and a reminder that single studies cannot prove or disprove phenomena in human science. However, two systematic reviews/ meta-analyses on this topic managed to cover almost all the current research on exactly this topic, specifically regarding procedure mask and N95 respirator use during physical activity for 60 minutes or less (5, 6). It is important to note that systematic reviews and meta-analyses are always considered at the top of hierarchies of evidence due to the systematic unbiased collation of evidence on a given topic.

  • Regarding gas exchange, authors concluded that masks do alter gas exchange (i.e., pulse, derived oxygen saturation, arterial CO2) and that higher intensity exercise led to greater adverse effects of the masks for gas exchange, however, provided the caveat that these effects are very small, occasionally perplexing (i.e., pulse derived oxygen saturation increasing with mask-wearing at rest) and did not seem to impact performance during the hour or less of activity.
  • Regarding breathing resistance, masks were found to lead to slower respiration rates and decreased ventilation alongside increased feelings of dyspnoea or ‘shortness of breath’ while wearing either mask; it was also noted that a high risk of bias was present in many of the included studies. Both meta-analyses showed that individuals wearing masks had higher perceived exertion during physical activity than their non-mask-wearing counterparts.

Overall, these thorough literature summaries on mask-wearing during physical activity (compared to no mask) reported variable results regarding changes in gas exchange but increased breathing resistance/ pulmonary difficulties and higher perceived exertion. However, the authors both concluded that the adverse effects of masks in these circumstances are negligible. It is important to remember that both of these reviews/ meta-analyses only included studies that looked at mask-wearing over the course of one hour or less.

Masks may be required to be worn for much more extended periods in many safety-critical work in areas such as mining, oil and gas, aviation, and rail, but to name a few. A scoping review by Kisielinski and colleagues (4) in 2021 encapsulated many more studies looking at the adverse effects of mask-wearing, including for several hours. The authors focused solely on negative consequences and found 44 papers demonstrating the significant negative impact of mask-wearing on a slew of outcomes collectively labelled Mask-Induced Exhaustion Syndrome (or MIES). Included in this review and within MIES is increased perceived fatigue/ exhaustion from prolonged use. In addition, a factor discussed in Kisielinski’s work is an increased risk of Hypercapnia (or a build-up in CO2) with prolonged use of mask used for individuals with obstructive sleep apnea (OSA). These two points were not considered within the two meta-analyses due to a focus on mask-wearing for less than one hour and only for ‘healthy’ individuals. However, in practice within safety-critical workplaces, mask-wearing rules/ mandates can result in wearing for much longer than one hour, and workers are not always free of sleep disorders such as OSA. For example, in a recent study in Western Australia, 31% of safety-critical workers were at risk for OSA (7). Given the risk that worker fatigue and reduced cognitive performance (a symptom of Hypercapnia) can pose, the adverse effects of mandatory prolonged use of mask-wearing should be carefully considered in safety-critical work environments.

Melius Consulting recommends that businesses investigate the individual impact of mask-wearing on safety-critical employees to minimise health and safety incidents. For example, mandatory prolonged use of masks throughout a shift up to 12 hrs may impact an employee’s perceived exertion/ fatigue rate and increase risk in a safety-critical role. Melius Consulting can assist businesses in determining individual variation on oxygen saturation levels, fatigue levels, sleep and wake behaviours, and the potential impact on performance.



  1. Prevention CfDCa. Types of Masks and Respirators Centers for Disease Control and Prevention: Centers for Disease Control and Prevention; 2022 [Available from:
  2. Kalra S, Chaudhary S, Kantroo V, Ahuja J. Mask fatigue. J Pak Med Assoc. 2020;70(12(b)):2484.
  3. De Brouwer C. Wearing a Mask, a Universal Solution Against COVID-19 or an Additional Health Risk? Available at SSRN 3676885. 2020.
  4. Kisielinski K, Giboni P, Prescher A, Klosterhalfen B, Graessel D, Funken S, et al. Is a Mask That Covers the Mouth and Nose Free from Undesirable Side Effects in Everyday Use and Free of Potential Hazards? International Journal of Environmental Research and Public Health. 2021;18(8):4344.
  5. Engeroff T, Groneberg DA, Niederer D. The Impact of Ubiquitous Face Masks and Filtering Face Piece Application During Rest, Work and Exercise on Gas Exchange, Pulmonary Function and Physical Performance: A Systematic Review with Meta-analysis. Sports Medicine – Open. 2021;7(1).
  6. Shaw KA, Zello GA, Butcher SJ, Ko JB, Bertrand L, Chilibeck PD. The impact of face masks on performance and physiological outcomes during exercise: A systematic review and meta-analysis. Applied Physiology, Nutrition, and Metabolism. 2021;46(7):693-703.
  7. Maisey G, Cattani M, Devine A, Lo J, Fu SC, Dunican IC. Digging for data: How sleep is losing out to roster design, sleep disorders, and lifestyle factors. Applied Ergonomics. 2022;99:103617.



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