Optochemical FFP2 mask alerts wearer when CO2 safe limit is exceeded

03 Feb 2022

University of Granada develops system based on novel gas sensor and signal processing electronics.

Scientists and engineers from the University of Granada, Spain, have developed and evaluated an “intelligent” FFP2 mask, which alerts the user through their mobile phone when safe limits of carbon dioxide (CO₂) are exceeded.

The team says this development solves an important problem since the pandemic began: “the CO₂ that we re-inhale inside our mask. When we use FFP2-type masks, a higher concentration of CO₂ is produced between the face and the mask than the ambient level (typically ~0.04%) due to the gas exhaled during breathing, the rebreathing of which causes adverse health effects, even in healthy people, such as discomfort, headache, fatigue, dizziness, sweating, increased heart rate, and muscle weakness.”

Furthermore, they say, it is known that these negative effects are related both to the duration of exposure and to the concentration of the gas itself. For example, some health regulations recommend a [safe] maximum value of 0.5% CO₂ in the workplace, or that a 30-minute exposure to 4% CO₂ is considered very harmful to health.

The intelligent FFP2 mask designed at Granada allows real-time determination of re-inhaled carbon dioxide using a mobile phone. This method represents a significant advance as a wearable system characterized by its low cost, scalability, reliability and comfort for monitoring magnitudes of interest for health.

The development has been achieved by the multidisciplinary research team ECsens between the departments of Analytical Chemistry and Electronics and Computer Technology of the UGR, which have together developed a real-time, battery-free, portable detection system for the measurement of gaseous CO₂ in said internal volume of the mask. The work is described in Nature Communications.

Optochemical sensor

Although standard masks simply act as air filters for the nasal and/or oral passages, the integration of sensors to measure parameters of interest is considered an added value to improve their use and effectiveness, creating a new paradigm of smart masks.

“The system that we propose consists of the inclusion, inside a standard FFP2 mask, of a flexible label made up of a novel optochemical CO₂ sensor of our own development together with all the signal processing electronics. Both have been printed on a light and flexible polymeric substrate, forming what is called a ‘sensor label’, without causing any discomfort for the user,” said the authors.

The manufactured tag does not use batteries, because it is wirelessly powered by the NFC communication link of a smart phone through an Android application. This app is also used for data processing, alert management, and display and sharing of results.

UGR scientists have carried out preliminary tests of this smart mask with subjects, both with sedentary activity and during physical exercise. “Our results, which are in line with previous clinical trials, provide CO₂ values between 2% during sedentary activities up to maximum values of almost 5% during high-intensity physical exercise,” said the authors.

“These values are significantly higher than the range of 0.04% – 0.1% of CO2 found in open atmosphere or typical work environments considered healthy. Although the tests carried out do not constitute a formal clinical trial, their purpose is to give an idea of the potential of the system developed in the field of wearable sensors for non-invasive health monitoring.”