Foxhole Wiki

This article is considered accurate for the current version (0.48) of the game.

When attached to a Gas Mask, this filter provides fresh air to the wearer.
In-game description

Gas Mask Filters (Filters for short) are items required to make the Gas Mask work. After taking in a certain amount of Green Ash, they will expire. They do not stack.

When equipping a Gas mask (in equipment slot 5), a filter will automatically be consumed by the mask, giving it a value of 100. When you get hit by Green Ash, the mask will decrease in filter points. When you are hit by Green Ash and the mask has no more points left, it will consume the first Filter from your inventory.

If you equip a Gas Mask and then put Filters in your backpack, these will not automatically be consumed. However, upon getting hit by Green Ash, they still get consumed as usual. If you need a free space in your inventory, you can also de-equip the mask and then re-equip the Gas Mask.

A single Filters will give the Gas Mask 100 hitpoints. When in a Green Ash cloud, these will quickly decrement by steps of 10. Sitting it out in a cloud for the full duration will cost 60% of a filter.