Air as a resource

There's plenty of building material in the atmosphere. SVG
(variable atmospheric humidity omitted)

With carbon dioxide CO₂ water H₂O and nitrogen gas N₂ one has hydrogen carbon oxygen and nitrogen (H C O N) available. Air can thus directly be used as building material.

Air can be used by:

• any AP small scale factory equipped with means of filtereing
• air using micro ships

Main compounds

The limiting gas is carbon dioxide. It is by far the most abundant one in the mix that can build higly stable three dimensional networked diamondoid materials. Others elements usable as parts for the structural core like Aluminum Silicon Titanium and more only form trace amounts of dust.

When one assumes a filtering efficiency near 100% one can extract around 1kg of carbon per hour with a middle sized blowing machine (of todays technology). When beta carbon nitride (Wikipedia) (which's properties are not well known yet) is used as structural material this mass roughly doubles. Structures of pure solid (sp³) nitrogen can be produced but they are higly explosive. (Easy production of explosives is one of APM's dangers.)

Argon as a noble gas does not form bonds. It may be used to fill Nanofactories at the lowest levels that need a vacuum equivalent environment.

Traces

Whats lacking most are heavier elements. Sulfur for example turned out to be useful for grooves in DMME bearings. It shouldn't be hard to get along without it though.

Traces of sulfur are present in the form of Wikipedia industrial activity has elevated the leves from below 4 ppt to above 7 ppt in the last sixteen years.