Some gas masks don't use filter canisters, but instead use cheek filter inserts. These function the same way as other filters (which is to say that it uses a particulate filter such as activated charcoal to filter out toxic agents), but instead of being contained in a canister, it is contained in a filter element that is placed inside the mask itself. Nicknamed the 'Porkchop' filter for its unique shape in some nations, a nickname can be applied to most cheek filter designs. The main drawback with this style of filter is that it is impossible to change the filters in any cheek-filter mask without taking the mask off; and given the amount of time it takes to properly install new cheek-filter elements, is very hazardous to undertake.
Notable masks to use the cheek-filters include the:
- M17, M17A1, and M17A2 and its copies: Polish MP-4 and MP-4B prototype, Bulgarian PDE-1, Czech M10 and M10M;
- Russian PMK-1 prototype;
While the filters for these masks are structurally similar, it should not be assumed that the filter components for any mask is compatible with other cheek-filter gas masks, particularly between with the various M17 copies.
A notable exception to the common style cheek-filter gas masks is the Chinese M65 Gas Mask, which, while technically being a mask that uses a cheek-filter, does not conform with the much more common 'M17-type' cheek filter gas masks, instead using a molded-in egg-shaped filter, which made the filter irreplaceable.