‘Smart’ FFP2 face mask alerts wearer when CO2 limits are exceeded

The mask design addresses a problem that has been highlighted since the Covid-19 pandemic began: that of the CO₂ that we rebreathe inside our face masks. Wearing FFP2-type face masks for any length of time produces a concentration of CO₂ between the face and the mask that is higher than the normal atmospheric concentration (~0.04 per cent), due to the gas we exhale when breathing. CO₂ rebreathing can cause adverse health effects, even in healthy people, such as general malaise, headaches, fatigue, shortness of breath, dizziness, sweating, increased heart rate, muscle weakness, and drowsiness.

These negative effects are known to be linked to both the duration of exposure and the concentration of the gas itself. For example, some health regulations recommend a maximum value of 0.5 per cent CO₂ in the working environment (averaged over an eight-hour day), or that a 30-minute exposure to 4 per cent CO₂ be considered very harmful to health.

The new FFP2 face mask designed at the UGR makes it possible to ascertain the level of CO₂ rebreathed in real time, using a smartphone application. This method – a wearable gas-monitoring system that is characterised by its low cost, scalability, reliability and convenience – represents a significant advance with important health benefits.

The study was conducted by the 'ECsens' multidisciplinary research team pertaining to the Departments of Analytical Chemistry and Electronics and Computer Technology of the UGR. Together, they developed the wireless, real-time, portable gas-detection system that monitors CO₂ levels inside the FFP2 face mask.

While standard face masks simply act as air filters for the nasal and/or mouth passage, the inclusion of sensors to measure specific parameters of interest provides added value that improves their use and effectiveness, creating this new ‘smart’ face mask.

The authors of the research wrote: “Since the global pandemic was declared by the World Health Organisation due to the spread of Covid-19, the universal use of face masks has been recommended or imposed among the general population, in a bid to prevent the rapid spread of SARS-CoV-2.

“Notwithstanding the generalised evidence in favour of face masks to reduce transmission throughout the population, there is also broad agreement on the possible adverse effects caused by their prolonged use, mainly as a consequence of the increase in respiratory resistance and the re-inhalation of the CO₂ that accumulates inside the mask”.

The system proposed by the team is based on inserting a flexible ‘tag’ into a standard FFP2 mask. This tag comprises an innovative, custom-developed opto-chemical CO₂ sensor, together with the necessary signal-processing electronics. Both the sensor and the circuitry are fabricated onto a lightweight, flexible polymeric substrate, forming the so-called ‘sensing tag’, which causes no discomfort to the wearer. The tag does not require batteries as it is powered wirelessly by the near-field communication (NFC) link to the smartphone – similar to that used for making wireless payments, for example – using an Android app. The custom-developed app is also used for data processing, alert management and display and sharing of results.

The UGR scientists conducted preliminary tests of the mask on subjects conducting both sedentary activity and those performing physical exercise. Describing their findings, they wrote: “Our results, which are in line with previous clinical trials, present CO₂ values of between 2 per cent during low work-rate (sedentary) activities and a peak value of almost 5 per cent during high-intensity physical exercise.

“These values are significantly higher than the typical range of 0.04-0.1 per cent of CO₂ found in atmospheric air or in typical work environments that are considered healthy. Although the performance tests we carried out do not constitute a formal clinical trial, they are intended to give an indication of the potential of this system in the field of wearable sensors for non-invasive health monitoring.”

The scientists emphasise that their face mask is also 100 per cent environmentally friendly, as it does not require batteries, relying instead on standard wireless smartphone technology.

The smart mask potentially has multiple applications in the fields of non-invasive health monitoring, pre-clinical research, and diagnostics using portable electronic devices. Other sensors could also be included, to detect other gases of interest.

The study – ‘Smart facemask for wireless CO₂ monitoring’ – has been published in the journal Nature Communications.