Oxygen-Expelling Mask
How it Works
The OEM is an airtight mask that fits around the mouth and nose of an angel. There are two types of OEMs. The first type is a self-contained OEM, which as a specific supply of air that is connected to the mask, allowing the person using it to breathe air of a certain oxygen content. The advantage of this mask is that it can be generalised to use for any species going anywhere with a different air environment than one's own. However, the downside is that it only supports so much use before needing to be refilled.The second type acutally filters the air, using materials that attract oxygen molecules but allow the rest of the air to pass. The little oxygen that is able to make it through is enough for the angel to breathe safely. The upside to this type of mask is that it lasts for far longer, however it comes with a disadvantage of having a reduced efficacy in even higher oxygen-rich environments, making it not 100% effective.
I really love the little detail that the masks are manufactured on the surface.
thanks! i wanted a way to explain why not many angels travelled down to the surface