# Zone Air System

This air system divides the station into impermeable areas called zones.

When something happens, i.e. a door opening or a wall being taken down, zones equalize and eventually merge.

Making an airtight area closes the connection again.

## Control Flow

**Every air tick**:

- Marked turfs are updated with update_air_properties(), followed by post_update_air_properties().
- Edges, including those generated by connections in the previous step, are processed. This is where gas is exchanged.
- Fire is processed.
- Marked zones have their air archived.

## Important Functions

**air_master.mark_for_update(turf)**
- When stuff happens, call this. It works on everything. You basically don't need to worry about any other functions besides CanPass().

## Notes for people who used ZAS before

- There is no connected_zones anymore.

- To get the zones that are connected to a zone, use this loop:

```
	for(var/connection_edge/zone/edge in zone.edges)
		var/zone/connected_zone = edge.get_connected_zone(zone)
```