Endgame Guide: Heat, Molten Metals & Cooling Tips

Endgame in Oxygen Not Included is the phase where volcanoes, high-temperature production, nuclear reactors, and scarce late-game materials dictate base design and long-term stability. The key challenges are managing intermittent high-power heat and molten metal outputs from Metal Volcanoes, building heat-tolerant infrastructure and buffers, processing high-temperature resources (kilns, refineries), and using endgame materials for durable, low-conductivity construction and heat sinks.

Volcano and Geyser Management

Metal Volcanoes eject molten metal and large quantities of heat during periodic ejection phases. They cycle through Dormant → Active (includes a short, intense Ejection Phase) → Idle. Design must treat ejection as a burst event rather than steady output.

• Buffer the heat: provide a high-thermal-capacity buffer adjacent to the volcano output to absorb the sudden heat spike and molten metal. Buffers can be large masses of high specific-heat materials or liquid thermal sinks.
• Rapid cooldown between ejections: during the Idle Phase move stored heat away from the buffer so it is ready for the next eruption. Passive heat diffusion is too slow; use engineered heat exchangers, cycling liquids, or scheduled heat pumps.
• Material choice: almost all Metal Volcanoes (except Niobium behaving differently) follow the same eruption timing and mass rules, but each metal differs in melting/freezing points and heat capacity — designs must match the specific metal to avoid wasteful cooling or melting of equipment.
• Avoid relying on Dormant time for cooling: the Dormant Phase is not guaranteed long enough to let an entire setup cool down.

Practical patterns:

• Contain eruptions in dedicated chambers isolated with high-temperature tiles.
• Let molten metal flow into insulated basins or liquid reservoirs where it solidifies safely and can be collected.
• Use automated gates/airlocks to protect duplicants and to control atmosphere around the ejection site.

Heat-sink and Thermal Management

Endgame heat sources include molten metal, refined production, kilns, refineries, and reactors. Effective thermal design combines material choice, insulation, and active heat transport.

• Insulation materials: use materials with the lowest thermal conductivity and high specific heat for walls around hot systems. Common choices:
  • Igneous rock: widely available and has one of the highest specific heats among common minerals.
  • Space-grade materials or Abyssalite (late-game) provide the best thermal isolation when available.
  • Ceramics (from Kiln or processed Clay) perform well as high-temperature structural tiles.
• Structural materials for high-heat equipment: use Thermium for heat-absorbing machines in the late game when available. Steel is a safe early/mid-game option but will underperform versus Thermium.
• Kilns and thermal economy: kilns can be run net heat-negative if fed with inputs above certain threshold temperatures. They exchange heat only with surrounding gas, not tiles they stand on, allowing vacuum placement for extreme-temperature production without overheating nearby structures.
• Refineries: crude oil is an effective heat sink. Refineries become net heat negative at moderate oil temperatures; supplying warm oil increases their cooling benefit.
• Ceramic production by heating Clay to very high temperatures will produce natural Ceramic tiles; mining those tiles causes mass loss, so this route is primarily useful only when other sources are unavailable.

Liquid and Mass Buffers

Use liquids and large-mass reservoirs as thermal buffers:

• Crude oil and other liquids with high heat capacity are excellent for absorbing and transporting heat. Route heat into a liquid loop and dump it into a controlled cold sink (radiator or space launch).
• Large solid masses (rock, Thermium blocks) act as passive heat reservoirs; design rooms with appropriate mass to smooth temperature spikes from volcanoes or reactors.

Nuclear and Meltdown Risks

Reactor systems are late-game power solutions but carry severe thermal and contamination risks:

• Enriched Uranium reactors will begin meltdown when fuel reaches extremely high temperatures; meltdown produces Corium debris, massive Radioactive Contaminants, Meteor Damage, and Nuclear Waste (including Nuclear Fallout). Reactor meltdown also temporarily doubles radiation emissions for a period while cooling.
• Always design reactors with redundant, high-capacity cooling systems and robust containment for potential corium and fallout.
• Place reactors in isolated, thermally buffered enclosures with active heat-transfer infrastructure capable of moving large heat loads away during peak events.

Germ and Biome Cleanup

Late-game disinfection and biome remediation are practical with gas choices and automation:

• Storing Slime and contaminated material in Chlorine atmosphere over a full cycle kills Slimelung, but human contact while handling will often spread contamination. Use Atmo Suits and Germ Sensors to automate disinfection and avoid duplicant infection.
• Beware that items like Deodorizers and Clay produced from Chlorine-treated Sand can retain germs and require careful handling or storage within the disinfecting atmosphere.

Material Economics and Conservation

Late-game materials are scarce and should be prioritized:

• Reserve Wolframite for Tungsten production; convert low-quantity ores into the most valuable end-use.
• Use Thermium for construction of heat-absorbing/high-durability equipment when possible.
• For devices exposed to huge heat loads (e.g., mass heat exchangers or vent systems), prioritize Thermium or other high-temperature materials; Steel is a fallback for earlier stages.

Automation and Operational Tips

• Automate cyclical cooling tasks: use sensors, automated pumps, and controlled valves to move heat into cold reservoirs during Idle phases.
• Use Atmo Suit automation and remote handling for hazardous cleanup and molten-metal collection.
• Monitor critical resource inventories (water, oil, coal/charcoal, food) during prolonged endgame operations; plan for material consumption and resupply.

When to Stop Expanding

If your goal is survival or to reach an achievement rather than full industrial scale, focus on essential life support and safety:

• Secure volcano/vent responses and reactor safety first.
• Once food and oxygen are stable and hazards contained, you may pause development and run at accelerated speed if you only need to survive to a target cycle.

This strategy synthesizes heat-first design, heavy use of thermal buffers and insulation, conservative use of scarce endgame materials, and automation to survive and exploit endgame hazards such as Metal Volcanoes and nuclear reactors.