Many reusable face coverings include a replacement filter pocket. A single filter is inserted into the replacement filter pocket to provide additional filtering properties to the face covering. Unlike the face covering, the filter is not able to be washed for reuse. Filters can though be used on more than one occasion. They commonly perform for up to 7 days at an average of 8 hours use per day. The frequency at which used filters should be replaced will depend on a number of factors including the length of time the filter is used, the breathing rate of the user, and the filtration requirement of the environment in which the filter is operating. Filters can be changed at other times if inhalation resistance increases when used. Filters offer respiratory protection from airborne contaminants and harmful particles including dust, pollution and respiratory droplets. They can be used when undertaking physical activities including cycling, hiking, and other outdoor activities.