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Can heated air filters trap and kill coronavirus?

Image credit: Volodymyr Byrdyak/Dreamstime

Researchers in the US have designed an air filter that can trap the virus responsible for Covid-19, killing it instantly.

Zhifeng Ren, director of the Texas Center for Superconductivity at the University of Houston (TcSUH), collaborated with Monzer Hourani, CEO of Houston-based medical real-estate development firm Medistar, and other researchers to design the filter. 

The researchers said that virus tests at the Galveston National Laboratory, Texas, found 99.8 per cent of the novel SARS-CoV-2 - the virus which causes Covid-19 - was killed in a single pass through a filter made from commercially available nickel foam heated to 200°C (392°F). It also killed 99.9 per cent of the anthrax spores in testing at the national lab, run by the University of Texas Medical Branch.

“This filter could be useful in airports and in aeroplanes, in office buildings, schools and cruise ships to stop the spread of Covid-19,” said Ren. “Its ability to help control the spread of the virus could be very useful for society.”

Ren added that Medistar executives have also proposed a desk-top model, capable of purifying the air in an office worker’s immediate surroundings. 

Covid-19 air filter

Image credit: University of Houston

Ren explained that TcSUH was approached by Medistar on 31 March - as the pandemic was rapidly spreading across the US - for help in developing the concept of a virus-trapping air filter.

With businesses reopening across the country, controlling the spread of the virus in air-conditioned spaces was urgent. The researchers were aware that the virus can remain in the air for around three hours, meaning a filter that could remove it quickly was a viable plan. 

Medistar said the virus cannot survive temperatures above 70°C, so the researchers decided to use a heated filter. By making the filter temperature far hotter - about 200°C - they were able to kill the virus almost instantly, the team said. 

During experiments, Ren suggested using nickel foam, saying it met several key requirements. It is porous, allowing the flow of air; electrically conductive, which allowed it to be heated; and is also flexible. 

The researchers stressed that nickel foam has low resistivity, making it difficult to raise the temperature high enough to quickly kill the virus. To tackle this issue, the team folded the foam, connecting multiple compartments with electrical wires to increase the resistance sufficiently to raise the temperature as high as 250°C. 

By making the filter electrically heated, rather than heating it from an external source, the team said they minimised the amount of heat that escaped from the filter, allowing the air conditioning to function with minimal strain.

Performance of prototype device on aerosolized SARS-CoV-2 and Bacillus anthracis.

Performance of prototype device on aerosolised SARS-CoV-2 and Bacillus anthracis, the agent of anthrax.

Image credit: University of Houston

A prototype was built by a local workshop and first tested at Ren’s lab for the relationship between voltage/current and temperature. It then went to the Galveston lab to be tested for its ability to kill the virus. Ren said it satisfies the requirements for conventional heating, ventilation and air conditioning (HVAC) systems.

“This novel biodefense indoor air protection technology offers the first-in-line prevention against environmentally mediated transmission of airborne SARS-CoV-2 and will be on the forefront of technologies available to combat the current pandemic and any future airborne biothreats in indoor environments," said Dr Faisal Cheema at the UH College of Medicine. 

Hourani and Dr Garrett K Peel from Medistar have called for a phased roll-out of the device, “beginning with high-priority venues, where essential workers are at elevated risk of exposure (particularly schools, hospitals and health care facilities, as well as public transit environments such as aeroplanes).”

According to Hourani and Peel, prioritising these sectors will both improve safety for frontline workers in essential industries and allow nonessential workers to return to public workspaces.

In April, scientists and engineers from Cambridge in the UK and Ma’alot-Tarshiha in Israel developed a carbon-based material that captures and destroys an animal coronavirus, a close relative of the SARS-CoV-2 virus strain.

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