Facemasks have been shown effective at filtering out viruses such as the SARS-CoV-2 virus, thereby reducing the risk of infection. Researchers hope to go one step further and create a mask that inactivates viruses using heat. The aim is to build masks that incorporate a heated copper mesh. As the person wearing the mask breathes in and out, air flows repeatedly across the mesh and any viral particles in the air are slowed and inactivated by the mesh and high temperatures. Such a mask could be useful for healthcare professionals as well as members of the public in situations where social distancing would be difficult to achieve such as a crowded bus.
The mask does not primarily block the virus. It actually lets the virus go through the mask but slows and inactivates it. Masks commonly worn are designed to capture some of the virus and while they do offer protection, they do not inactivate the virus and sterilize the air. The team set out to design a mask that would kill viruses using heat. They used copper mesh as the heating and capture element and performed some mathematical modeling to determine the optimal temperature range they would need to achieve to kill coronaviruses flowing inward or outward from natural breathing.
The researchers calculated how rapidly coronaviruses degrade at different temperatures and trapping conditions and found that a temperature of about 90 °C could achieve between a thousandfold and millionfold reduction in viral particles, depending on the final mask size. The temperature can be achieved by running an electrical current across a 0.1-mm-thick copper mesh or thermoelectric heater powered by a small battery. The current prototypes include a 9-volt battery, which would provide enough power to heat the mask for a few hours and would cool the air before it is inhaled.
The team enhanced the efficiency of virus deactivation by taking advantage of the breath to create a type of reactor known as a reverse-flow reactor. As the person wearing the mask breathes in and out, the airflow continually reverses, allowing any viruses in the mask to pass over the mesh many times and making it more likely that they will be deactivated. Purified air flows out of vents on both sides of the mask. The copper mesh is surrounded by neoprene, an insulating material that prevents the outside of the mask from becoming too hot to wear.
N95 respirators, surgical masks, and cloth masks are effective and should be used during the pandemic as directed but one potential advantage of heated masks is that because they kill the virus, they don’t need to be decontaminated or thrown away after use. Additionally, they may offer extra protection by eliminating the virus rather than only filtering it. The new mask enables the wearer to breathe in medically sterile air and breathe out medically sterile air, protecting people nearby. Heated masks would be more expensive than cloth masks or surgical masks but they may be useful in situations where exposure risk is high and cost is less of a concern.