Portable Air Scrubber

The portable air scrubber is filtration for the early game: you put it in a room, insert a battery and filters, and it pulls the matching gases out of the air. It needs no pipes, cables or data network.

Its slots:

• slot 0: a battery,
• slots 1 and 2: one gas filter each, such as Filter (Carbon Dioxide) or Filter (Pollutant).

It takes no canister. Whatever the filters catch is collected in its inner tank of 250 litres; the rest of the air it draws in goes straight back. It works on its own cell and the open neighbouring cells. Without filters it sucks in everything it gets – that empties a room instead of cleaning it.

According to the game code, three things stop it:

• The inner tank is above 8,106 kPa. It then reports overpressure. Hook it up to a connector for portable devices and drain the tank into a pipe network, or open it (Open) – it then gradually releases its contents into the room and does not filter in the meantime.
• A filter is empty. A single used-up filter stops the whole device, even if the second one still has reserve.
• The battery is empty. It draws 25 J per tick.

A calculation: a room of four cells at 100 kPa containing 2 % Pollutant holds about 26 mol of it – a partial pressure of 2 kPa, twice the damage threshold of 1 kPa. At 20 °C the inner tank holds about 830 mol up to its limit, plenty for this room. Only below a 0.5 % share, i.e. 0.5 kPa, is the room safe again.

The filter reserve drops by 1 after every 145 ticks in which a filter actually catches something. The scrubber has no logic to report that; on the fixed Filtration you read the reserve through slot logic. For running a base long-term, a fixed system pays off, see Filtration: separating gases, changing filters, getting rid of waste gases.