November 2024: Hooman Tafreshi

Professor, Department of Mechanical and Aerospace Engineering, NC State University

Improving the Use of Personal Protective Equipment

“Yes, Covid is gone, but we never know if there is another pandemic around the corner. Quality of air is becoming more of an important thing every day. People are realizing that we pay so much attention to the water we drink. We have bottled water, because we care about the quality of water, but we don’t have bottled air. We take it for granted that the air is clean, which is not always the case. So now people are learning that quality of air also matters.”

Hooman Tafreshi

With the spread of the COVID-19 pandemic came a cascade of extensive research across various fields, one of which included the filters used in personal protective equipment (PPE). Face masks and filters became critical to public health and stopping the transmission of COVID-19.

But now that the pandemic has subsided, why continue the research? Protective face masks and air filters have proven to be efficient tools for reducing the spread of not only COVID-19, but other airborne respiratory diseases. As we face the possibility of new variants or infectious diseases, future research on masks and filters will ensure that we are equipped with the best practices to protect and prevent in the future. On top of this, filters are used in everyday life to guard against harmful air pollutants, ones that we didn’t even know surround us. Clean air is key to overall public health.

It is critical to understand the varying effectiveness of different filter types to better inform and prepare the future populations. Dr. Tafreshi and his team at the Nonwoven Institute at North Carolina State University are examining the most efficient ways to electrostatically charge filters and masks, with the goals of improving the overall effectiveness of these filters and changing the way we view air quality.

You are the lead PI on two Personal Protection Equipment projects, Smart Manufacturing of PPE and HVAC Filters and Next Generation Respirators. How and why did you develop these projects?

You’re familiar with COVID, the shortages of face masks, and other issues related to the pandemic. I have a background in fluid mechanics and aerosol flow simulations and have done a lot of work in that area. I also work with the Nonwoven Institute (NWI), an institute well equipped with manufacturing equipment for making nonwoven materials, which are used in face masks, HVAC filters, and more. So, it would be a perfect combination for us to put this computational expertise that I had, and the manufacturing capabilities of the NWI so that we could propose solutions to the problems that exist in current, and especially in that time, face masks and their performance. And because face masks are filters, what we learn from face mask operation also applies to an HVAC filter.

Your projects research the different charging techniques for masks and filters. What are these techniques and how do they work?

What you probably don’t notice in a typical facemask is that it is electrostatically charged. Without the charge, a face mask doesn’t capture much. The charge is added to a normal mechanical filter to allow the filter to capture more particles through electrostatic attraction force, just like a magnet attracts a small piece of metal. An electrostatically charged filter attracts aerial particles in the air and captures them. It does it without needing to be extremely dense, and when it’s not very dense, it is more breathable. So, you can breathe through it and be comfortable, while at the same time receiving protection. This is the reason why charge is important. Without the charge a cloth mask and a non-woven mask are not too different from one another.

What are the main takeaways or key pieces of information that you’ve learned so far that you wish to share with the public?

If I just want to put everything like in a quick summary, we are learning about these 2 main processes. One is called corona charging, which uses a high intensity electrostatic field to induce charges on the material. And the other one is called hydro charging, where you use water, as simply as it is, to create charge in the material. So hydro charging and corona charging are the 2 main leading mechanisms for charging. We are quantifying how charging parameters can impact performance of ability and developing predictive models for these 2 systems. We have made a lot more progress with corona charging.

What is the value of this research, and why is it important to continue researching better forms of PPE, even as the threat of COVID dissipates?

If we know how to make better face masks, it’s going to prepare us for the next pandemic. And whatever we learn from producing better face masks, can then be applied to making better HVAC filters for buildings. You don’t just need filters for a pandemic. You need quality filters where you have pollen or smoke in the air, or when you have glue and paint in classrooms; the list goes on. So, we’re not always looking for filtration because we want to handle the pandemic situation. Sometimes in the normal flu season, you need better filters in your house. The research we’re doing is starting another, bigger and much more impactful phase that is changing how indoor air quality is monitored and controlled.