Rust Deoxidizer

Rust Deoxidizer is a refining building that converts Rust and Salt into Oxygen and Chlorine Gas. It is one of the few early-mid game ways to produce Oxygen without using water, and it is also a source of Chlorine Gas, which can be useful or troublesome depending on how you handle the exhaust.

When operating normally, the Rust Deoxidizer consumes 750 g/s of Rust and 250 g/s of Salt while the surrounding pressure is at or below 1800 g. It produces 400 g/s of Oxygen into the building’s storage and emits gas from its output tile, with the two gas products appearing in the same game tick. Like other one-tile gas emitters, the produced gas will merge with matching gas in adjacent tiles, displace what is already in the output tile, or otherwise exchange mass with it if the tile is occupied. If the average temperature of the inputs is above 75°C, the outputs inherit that average temperature; otherwise, the outputs are fixed at 75°C. The building also creates more total heat capacity in its products than it consumes from its inputs, so it effectively generates heat.

The building has large internal storage, holding up to 585 kg of Rust and 195 kg of Salt. Once one of those inputs falls below one third of capacity, the building will request delivery so a Duplicant can replenish it. If the stored Rust reaches 24 kg, it falls out of the output tile as debris.

A key practical issue is the Chlorine Gas output. Nearby Dasha Saltvine can absorb it, and a Rust Deoxidizer running continuously requires exactly 5 Dasha Saltvines to remove all of the Chlorine Gas it produces. If those Saltvines are domesticated, this setup recovers about 36% of the spent Salt; with wild Dasha Saltvine, the recovery is only 6%. This makes Saltvine placement an important consideration if you want to run Rust Deoxidizers as a sealed oxygen system.

If your goal is only to obtain iron, direct melting of Rust into Molten Iron and then solidifying it into Iron can achieve 100% conversion and avoids using the Rust Deoxidizer entirely. That route is preferred when the extra Oxygen and Chlorine are not needed.