---
title: emissionDurationVariation
framework: scenekit
role: symbol
role_heading: Instance Property
path: scenekit/scnparticlesystem/emissiondurationvariation
---

# emissionDurationVariation

The range, in seconds, of randomized emission duration values. Animatable.

## Declaration

```swift
var emissionDurationVariation: CGFloat { get set }
```

## Discussion

Discussion Setting a nonzero value for this property randomizes the effect of the emissionDuration property. For each emission period, SceneKit randomly adjusts the duration by up to half the emissionDurationVariation value. For example, if the emissionDuration value is 1.0 seconds and the emissionDurationVariation value is 0.5 seconds, the system emits particles over a period of 0.75 to 1.25 seconds before stopping. The default value is 0.0 seconds, specifying no randomization. You can animate changes to this property’s value. See Animating SceneKit Content.

## See Also

### Managing Particle Emission Timing

- [emissionDuration](scenekit/scnparticlesystem/emissionduration.md)
- [idleDuration](scenekit/scnparticlesystem/idleduration.md)
- [idleDurationVariation](scenekit/scnparticlesystem/idledurationvariation.md)
- [loops](scenekit/scnparticlesystem/loops.md)
- [warmupDuration](scenekit/scnparticlesystem/warmupduration.md)
- [birthRate](scenekit/scnparticlesystem/birthrate.md)
- [birthRateVariation](scenekit/scnparticlesystem/birthratevariation.md)