Respirators of N-95. To combat a shortage of these masks during the Covid-19 pandemic, new research … [+]
In the face of demand caused by the Covid-19 pandemic, the Centers for Disease Control have devised strategies to optimize the supply of N95 respirators, one of the most popular pieces of PPE. Healthcare professionals are often expected to use their N95 masks multiple times before leaving. However, the masks can become infected during interactions with patients with coronavirus, which puts the wearer at risk of contracting the virus if they remove and re-apply the mask many times.
The solution to mitigating the risk posed by reunion can be found in an unexpected place – your kitchen!
Research shows that N95 masks can be effectively decontaminated with electric cookers. A new paper from researchers at the University of Illinois describes how the team used an electric cooker to provide N95 respirators with dry heat treatments that disinfect them without compromising their efficiency.
Back in February, before coronavirus lockon began to sweep into the United States, researchers from Chung Shan Medical University in Taiwan experimented with a variety of possible sterilization methods for N95 respirators. Their results caused the masks to soak in bleach as alcohol drastically reduced their filter effectiveness. However, in a rice cooler, they heat the masks effectively sterilizing while filtering out the least amount of damage from any other method tested.
Taiwanese Health Minister Chen Shih-chung even promoted the method for rice cookers by demonstrating it at a Central Epidemic Command Center press conference in April. In July, scientists from Case Western Reserve University wrote about their results from using a rice cooker as a decontaminant. They suggested that the answer was not about heat but humidity, and said that steam cooking could effectively deactivate viruses on dust masks.
Researchers from the University of Illinois differentiated their study from previous research by emphasizing and testing according to the four recommendations for reuse of N95 respirator, developed by 3M, the main manufacturer of the popular mask.
For successful decontamination, 3M states that the method must inactivate the target virus, not cause damage to infiltration, not affect fit, and leave no potentially harmful chemicals to the wearer.
The researchers used a Faberware pressure cooker – a relatively inexpensive and common device – for the experiments. They performed the tests on four different viruses, including Tulane virus and rotavirus, to see how effective the method is at decontamination. The team put the viruses on the belt of the mask, inside, inside, outside edge and outside.
After 50 minutes on the heat of 100 degrees Celsius in the electric cooker, they calculated all the viruses on the masks had experienced a decrease in the integrity of the binding protein and the capsid protein – the shell that contains the genetic material of it encloses the virus. They found that each test virus was inactivated by at least 99.9 percent during the course of treatment.
Before being placed in the electric cooker, the N95 had a more than 99 percent efficiency in filtering particles. After 20 cycles of 50 minutes of dry heat treatments in the pressure cooker, the efficiency dropped only to 95 percent.
To ensure that the 20 cycles of treatment did not significantly change the fit of the respirators, the researchers put the treated masks through strict fit tests. Participants carried the treated N95 respirators in a test room filled with sodium chloride (NaCl) aerosol and completed a series of exercises, including talking, turning their heads from side to side and nodding. Afterwards, the ratio of the NaCl concentration in the air to that inside the mask was measured. Each mask had a calculated fit factor of greater than 100 – a continuous class for the test.
For those who want to treat their respirators at home in electric cookers, the researchers have posted a YouTube video describing the process. They suggest covering the tube with a towel because the temperatures of the interior walls become hot enough to melt and damage the respirators when they come in direct contact. The video also notes that several masks can be disinfected in the cooker at the same time.
This study may be particularly useful for health care workers, although the researchers noted that further testing is needed on different types of respirators, as different materials may require different temperatures and times for decontamination.
