In the current health emergency, each of us needs patience in order to play our part in stopping COVID-19 spread. More than 930,000 people worldwide have been infected by the deadly virus and over 47,000 have died.
Besides washing your hands frequently, it is extremely necessary that you clean your house and practice social distance and that you use a face mask when you leave. With readily available supplies, you can make masks and desinfectants in your home.
You might be wondering how many times a mask can be used or whether a mask can be disinfected for reuse or not.
As per a study ‘Addressing COVID–19 Face Mask Shortages’ published by the Stanford Medicine Anesthesia Informatics and Media Lab, here are the questions and answers that you need to read in this regard:
Question: Can N95 masks be reused multiple times and remain effective barrier protection for SARS–CoV–2?
Answer: Although this process is used according to CDC when there are PPE shortages. It is not safe and there is no high–level evidence to indicate this is safe. We could find no reassuring statistics released by the CDC or others during other pandemics to show this practice is safe and the barrier protection is shown to deteriorate with use and time.
The second question:
Question: Can N95 masks be autoclaved or sterilized by other means for safe reuse?
Answer: To be useful, a decontamination method must eliminate the viral threat, be harmless to end-users, and retain respirator integrity.
To clean your masks, you can use a number of decontamination methods such as 70 degrees Celsius hot air in an oven, hot water vapors, ultraviolet light, 75% alcohol, and chlorine-based disinfection among others.
Let’s have a look at how effective these methods are as per the experiments performed by the 4C Air.
| Samples | Meltblown Fiber Filtration | Static–charged Cotton | E. Coli. Disinfection Efficiency | ||
| Filtration Efficiency (%) | Pressure Drop (Pa) | Filtration Efficiency (%) | Pressure Drop (Pa) | ||
| 70°C hot air in oven, 30 min | 96.60 | 8.00 | 70.16 | 4.67 | >99% |
| UV light, 30 min | 95.50 | 7.00 | 77.72 | 6.00 | >99% |
| 75% alcohol, soaking, and drying | 56.33 | 7.67 | 29.24 | 5.33 | >99% |
| Chlorine-based disinfection, 5 min | 73.11 | 9.00 | 57.33 | 7.00 | >99% |
| Hot water vapor from boiling water, 10min | 94.74 | 8.00 | 77.65 | 7.00 | >99% |
| Initial samples before treatment | 96.76 | 8.33 | 78.01 | 5.33 |
Note: The experiments are known to kill all coronaviruses, however, the tests were performed on E. Coli as an accepted protocol.
The above table shows that while the other methods are useful, alcohol and chlorine cannot be used for cleaning masks. These will remove the static charge in the microfibers in N95 facial masks, reducing filtration efficiency. In addition, chlorine also retains gas after de-contamination and these fumes may be harmful to users.
Other Methods
In another study, 5 methods were used such as:
- bleach,
- ethylene oxide (EtO),
- microwave oven irradiation,
- ultraviolet germicidal irradiation (UVGI),
- hydrogen peroxide (vaporized and liquid forms).
Bleach and microwave didn’t work because the bleach gases cause irritation whereas microwave heating melts the mask.
