Summary decided to design this face mask due their short supply here in Italy occurred during COVID 19 outbreak. It should somehow protect nose-mouth area, but it lacks of any certification so I decline any responsibility for their misuse, you wear it at your own risk but for sure they're better than wearing no mask. The design consists of two parts that need to be paired together: Outer Shell - Inner shell The inner shell has a airway hole which needs to be sealed off using a material with a fair degree of water permeability such as non-woven fabrics fastened with a simple rubber band around the hole edge or even better, if available, cutout of HEPA or activated carbon filter usually used in kitchen hoods or air conditioning. Rubber bands need also be used to strap the mask to your face, by exploiting the holes on the sides of the outer shell. The filter needs to be replaced often and it depends on the type of filter you choose, since the mask is reusable it needs to be sanitized every time you replace it.