Oxygen Mask
The Oxygen Mask is the simplest, cheapest craftable Exosuit produced by the Crafting Station. It protects Duplicants from hostile environments at the cost of Athletics. Dupes equip an Oxygen Mask if one is available at an Oxygen Mask Dock. Dupes also cannot pass an Oxygen Mask Checkpoint if they aren't wearing an Oxygen Mask.
Oxygen Masks are crafted at a with 50 kg Aluminum, Cobalt, Copper, or Iron Ore or 1 Worn Oxygen Mask.
Hazard Protection
Oxygen Masks protect their wearer against Yucky Lungs and inhaling Germs, but not Eye Irritation or Popped Eardrums. Oxygen masks do not protect the wearer from Gnit stings.
Oxygen Masks provide their wearers with Oxygen, allowing them to work in non-oxygen environments without any worry. At 20 kg capacity, a dupe with average oxygen consumption may breathe for 200 seconds before needing to hold their breath. However, dupes will retreat to refill their Oxygen Mask at ?% capacity.
Drawbacks
Oxygen Masks apply -2 Athletics while worn. This penalty can be negated with the Suit Sustainability Training skill.
Oxygen Masks lose durability at a rate of 20% per cycle while worn, and will turn into a Worn Oxygen Mask when an Oxygen Mask with 0% durability has been unequipped.
Duplicants will still exhale 
Carbon Dioxide 
(2 g/s) into nonbreathable areas, which is problematic when trying to maintain a 
Vacuum or keeping an area free of Carbon Dioxide.
Notes
- Oxygen Masks have a significantly smaller oxygen capacity compared to an Atmo Suit, lasting only 200 seconds. (⅓ cycle)
- Oxygen Masks have a limited durability and must be repaired after their durability falls to zero.