# External Forces module reference

> Explore properties on the External Forces module, to configure the effect of external physics forces such as wind zones and force fields on particles emitted by the system.

This property modifies the effect of **wind zones** and [Particle System Force Fields](/engine/6000.3/manual/visual-effects/particle-systems/configuring-particles/class-particle-system-force-field.md) on particles emitted by the system.

## Properties

For some properties in this section, you can use different modes to set their value. For information on the modes you can use, refer to [Vary Particle System properties over time](/engine/6000.3/manual/visual-effects/particle-systems/varying-particle-system-properties-over-time.md.md).

| ***Property***       | ***Function***                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                            |
| -------------------- | --------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |
| **Multiplier**       | Scale value applied to wind zone forces.                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                  |
| **Influence Filter** | Choose whether to include Force Fields based on a **Layer Mask**, or via an explicit **List**.                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                            |
| **List**             | Define an explicit list of Force Fields that can affect this Particle System. This appears when the **Influence Filter** is set to **List**.                                                                                                                                                                                                                                                                                                                                                                                                                                                              |
| **Influence Mask**   | Use a Layer Mask to determine which Force Fields affect this Particle System. This appears when the **Influence Filter** is set to **Layer Mask**.This property has the following options:**Nothing**: Automatically unticks all other options, turning them off**Everything** (default): Automatically ticks all other options, turning them on**Default****TransparentFX****Ignore [Raycast](https://docs.unity3d.com/Packages/com.unity.ugui@latest?subfolder=/manual/Raycasters.html)****Water****UI****[PostProcessing](/engine/6000.3/manual/post-processing-and-full-screen-effects/overview.md)** |

## Additional resources

* [Particle physics forces](/engine/6000.3/manual/particle-physics-forces.md)