Viscous filters employ a sticky coating to capture airborne dust and particles. These filters are generally cleaned and reused instead of being completely discarded. They can be categorized as dry type (lacking an oil coating) or automatic type (self-cleaning). Maintenance can also involve manually cleaning by washing or substituting the sticky medium. However, they are not typically designed as fully replaceable type, unlike disposable filters that are discarded after use. Consequently, the term 'replaceable type' is inconsistent with the fundamental design of a viscous filter.