Nest Alert

Know when the biters are coming. A dedicated combinator detects if nests are in your pollution cloud — connect it to a speaker and be prepared. Optionally marks the consuming nests directly on the map.

Who is this for?

Nest Alert is designed for the early and mid game — especially for players who like a small pollution cloud and who don’t want to build a large perimeter defence. If your defense philosophy is Offense is the best defense, you need to know the moment a nest starts feeding on your pollution. This mod gives you exactly that signal.
All you have to do is find the nests.

Spawner Detection

The combinator reads the pollution consumed by enemy spawners on its surface every 5 seconds. It works on:

Nauvis — biter and spitter spawners
Gleba — stomper, wriggler and strafer spawners
Any modded planets — all entities of type unit-spawner are automatically detected, no configuration needed

How to Use It

Craft a Nest Alert Combinator (same recipe as the constant combinator, unlocked with Circuit Network).
Place it anywhere on your factory. It automatically contains the Nest Pollution Consumption signal.
Connect it with a red or green wire to a Programmable Speaker.
Configure the Speaker: set it to play an alert when the Nest Pollution Consumption Signal is > 0. That's it — the moment any spawner within your pollution cloud starts consuming pollution, the alarm sounds.

The Nest Alert Combinator also works as a normal constant combinator.

How It Works (Technical)

Every 300 ticks (5 seconds) the mod reads Factorio's built-in pollution_statistics for the surface the combinator is placed on. It sums up the pollution consumption across all detected spawner types and writes the result into the Nest Pollution Consumption signal slot of the combinator.

UPS impact: negligible. The poll happens once per 5 seconds, not every tick. The pollution statistics are already tracked by the game engine — the mod just reads a number that already exists.
No hidden overhead: no entity scanning, no pathfinding, no per-tick hooks.
Multi-surface support: each combinator reads only its own surface. Place one on Nauvis, one on Gleba — they work independently.

Is This Cheating?

No. Or yes?!?

The exact same information — how much pollution each spawner type is consuming — has always been available in Factorio's production statistics screen, under the pollution tab, visible to every player at any time, in any save, without any mod. You could manually check it every few minutes and achieve the same early warning. The only difference is that doing so manually is tedious and easy to forget.

This mod automates the tedium. And automation is, as you may have noticed, quite literally what this game is about.

The cheat mode described below is a different matter — that one genuinely is a cheat, which is why it ships disabled.

Cheat Mode (optional, off by default)

Everything above tells you that a nest is eating your pollution. Cheat mode tells you where. Set [CHEAT] Show nests in the mod settings to Enabled every chunk that currently feeds a nest gets marked in the map view.

This is deliberately labelled as a cheat: unlike the combinator, it gives you information the game does not offer without mods. It is a separate, opt-in switch — the combinator works exactly the same whether cheat mode is on or off. Also, the cheat mode works even without the Nest-Alert Combinator.

Two settings control it, both changeable in-game without a restart:

Show nests — Disabled, Enabled: explored area only, or Enabled: explored and unexplored area.
Map display — Map icon, Alert, or Map icon and alert. The map icon is a map tag and can be edited or deleted. Deleted tags do not reappear. The alert shows in the alert bar, blinks on the map, and clicking it jumps to the nest.

Only spawners that really absorb the surface's pollutant get marked. Not every spawner does — the small Gleba spawner, for example, absorbs nothing and never shows up.

AI

Mod concept & design by Morlot.
Implementation developed with the help of Claude (AI assistant by Anthropic).