Non-medical face masks or face coverings should:

• allow for easy breathing
• fit securely to the head 
• maintain their shape after washing and drying
• be changed if damp or dirty
• be comfortable and not require frequent adjustment
• be made of at least 2 layers of tightly woven material fabric (such as cotton or linen) plus a third non-woven layer
• be large enough to completely and comfortably cover the nose and mouth without gaping