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.

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

1. Craft a Nest Alert Combinator (same recipe as the constant combinator, unlocked with Circuit Network).
2. Place it anywhere on your factory. It automatically contains the Nest Pollution Consumption signal.
3. Connect it with a red or green wire to a Programmable Speaker.
4. 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.

Credits

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