Background: Breathable air has specific ranges of content of oxygen, nitrogen, water and carbon dioxide.

http://www.livescience.com/technology/050718_station_air.html

Business Services:

• Sell new air created by purchase of LLOXLunar_Boom_Town/LOX_Domestic_and_Exports, Liquid NitrogenLunar_Boom_Town/Nitrogen_commodity_imports_and_futures, Water, and mix to advertised composition of fresh, new air products.
• Receive used air and recondition and deliver fresh air back to the customer via either bottle or airline.

Air Scrubber Technology sounds like a spray nozzle, algae aquarium, and appropriate circulation, harvesting, back flush or filter scrubbing processes. Algae --> Fertilizer/Methane Digester or perhaps ethnanol/animal feed.

• Monitor and alert for dangerous breathing conditions.
• Sell excess H2O, CO2, impurities extracted from used air.

Pricing: Could be by volume of air processed or delivered or number of people/animals/plants serviced for a specified time period.

Capital Required: Air processing equipment. Gas reserve storage for O2,N,H2O,CO2. Air line or bottle delivery. Telemetry monitoring.

Possibly applicable technologies:

Acquiring initial and makeup stock of oxygen:

• http://ares.jsc.nasa.gov/HumanExplore/Exploration/EXLibrary/DOCS/EIC034.HTML

Acquiring initial and makeup stock of nitrogen:

• Import from Earth
• Recover from Earth imported materials ... i.e. food, fabric, cleaners, etc.