Yes they are safe to use.
A mask or face covering can be homemade or purchased, and should:
- be made of at least 3 layers
- 2 layers should be tightly woven material fabric, such as cotton or linen
the third (middle) layer should be a filter-type fabric, such as non-woven polypropylene fabric - be large enough to completely and comfortably cover the nose, mouth and chin without gaping
- allow for easy breathing
- fit securely to the head with ties or ear loops
- be comfortable and not require frequent adjustments
- be changed as soon as possible if damp or dirty
- maintain its shape after washing and drying
