Washing

One advantage of cloth masks is that they can be washed and reused. We don’t know how often it’s necessary to wash cloth masks used in community settings. We suggest washing if it is visibly soiled, or after each 8 hours of use, recognizing that this is arbitrary. Change it if becomes damp; it can be dried in a paper bag.

Effect of washing on filtration

Cotton and industry-grade spunbond polypropylene are both intended to be washed in normal use. However, we do not know how their filtration properties are altered by washing or repeated washing. Polypropylene is plastic, stable to 50 degree celsius in a hot wash, but perhaps not stable at tumble-dryer temperatures, and definitely should not be ironed. The physical effects of washing on polypropylene might include generation of microplastics (most of which would contaminate waste water rather than remain on the mask) and the degradation of filtration properties.

Washing disposable masks resulted in variable loss of efficiency.

Using a washing machine

Cloth masks can be laundered in a washing machine, provided the fabric is suitable for machine washing. If possible use a mesh bag to protect the mask in the washing machine, handle carefully at all times and check that the shape is retained following washing. Be especially gentle with masks including nose wires. Masks should be designed so these can easily be replaced. Do not microwave masks containing metal.

Studies by the EPA using a hot (50 degree celsius) with standard domestic detergent showed effective cleaning, tested with a surrogate virus, similar to SARS-CoV2.

A 2020 review summarizes what is known about persistence of pathogens on textiles.

Hand washing

If you are hand washing, use warm water and soap or detergent (eg, clothes-washing liquid or dish-washing liquid), increase the exposure to detergent and heat by leaving it to soak in hot soapy water. Rinse the mask thoroughly before drying.

​Caring for masks containing polypropylene

Masks that contain non-woven industry-grade spunbond polypropylene or rectangles of this material used as filters can be hot washed with detergent in a washing machine. You can wash the filter right in the mask, though it may become separated in the wash. Reshape masks when damp and hang to dry. Polypropylene should not be tumble-dried or ironed: it is plastic and will melt.

Caring for nosewires

Nosewires can degrade and penetrate material with repeated laundering, especially by machine. A mesh bag may provide a degree of protection. Inspect the clean masks before giving them to children or putting them on yourself.

​Bleach

Bleach, as expected, was effective in cleaning in studies by the EPA, using a surrogate virus, similar to SARS-CoV2. We don’t recommend bleach because of concerns about adequate rinsing and possible inhalation hazards.