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 an adsorption 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.