If, like many people, you wear face masks in public, this simple homemade mask hack will increase your ability to filter out small particles in the air. All you need is a pair of pantyhose or nylon stockings.

Due to the shortage of N95 masks and medical masks required for healthcare workers, the Centers for Disease Control and Prevention has issued an advisory for Americans to wear cloth face covers in public places. Many people are learning how to make face masks at home or finding places to purchase face masks online.

Now, a Northeastern University study has found a way to make those homemade cloth masks even more effective against such small air particles that can carry COVID-19.

The researchers found that adding an outer layer made from nylon stockings provided a better seal and in some cases was as effective or more effective than medical surgical masks.

The study has not yet been peer-reviewed, but has been posted on the university's website and on the scientific preprint site medRxiv in order to share information quickly.

The researchers measured the ability of various masks to block particles ranging from 20 nanometers to 1,000 nanometers in diameter (the coronavirus that causes COVID-19 is about 60 to 140 nanometers).

The researchers added to the various masks a nylon stocking overlay made by cutting a ring of material about 8 to 10 inches high from one leg of a pantyhose. When that ring is placed over the head and pulled down over the mask, it fits snugly over the face. This tight fit would allow particles that might otherwise be inhaled around the loose edges of the mask to be filtered through the mask instead.

The addition of pantyhose rings improved the effectiveness of the cloth mask by 15% to 50%.

The stocking layer even improved the performance of 3M surgical masks. According to the study, it went from blocking 75% of particles to 90%. This is almost as effective as the N95 respirator, which blocks 95% of particles.