Depth filters are the variety of filter

Filter (chemistry)

In chemistry and common usage, a filter is a device that is designed to physically block certain objects or substances while letting others through. Filters are often used to remove solid substances suspended in fluids, for example to remove air pollution, to make water drinkable, and to prepare...

s that use a porous filtration medium to retain particles throughout the medium, rather that just on the surface of the medium. These filters are commonly used when the fluid

Fluid

In physics, a fluid is a substance that continually deforms under an applied shear stress. Fluids are a subset of the phases of matter and include liquids, gases, plasmas and, to some extent, plastic solids....

to be filtered contains a high load of particles because, relative to other types of filters, they can retain a large mass of particles before becoming clogged.