Air Filter
Your air filter timer is the most important piece of information visible on Artyom’s gear. You can see it visible on his left arm, and the timer will count down only when you’re in an area with toxic air. If the timer is not going down, this means you can take your gas mask off by holding down on the directional pad.
If you hear a high-pitched beep and see a notification to change your filter, it means you have less than one minute remaining before it will be completely worn out. You can craft more whenever you want, and certain key areas will also occasionally offer air filters are loot.
Compass
Early in Metro Exodus, you’ll also gain access to a compass, visible on Artyom’s left arm, that points you in the direction of your main objective. If you don’t have time to pull out the map and want to instead follow the main storyline only, you can use it and keep up the pace. Later on, you’ll get the option to replace it with a small radar device that will beep and point out the location of nearby lifeforms.