On the device itself:

If you know why the alarm is sounding, and you can verify that it is not a life-threatening situation, you can push the button on the initiating unit (green LED flashing every second) to silence the alarm for 8-10 minutes. If the smoke is not too dense, that unit and all interconnected units will silence. After the Hush period, the smoke alarm will automatically reset and sound the alarm if particles of combustion are still present. You can use Hush repeatedly until the air has been cleared of the condition causing the alarm.

In the Kidde app:

When a smoke alarm event occurs, the app will show the name of the alarming unit and give an option to Smart Hush the smoke alarm. If you know why the alarm is sounding, and you can verify that it is not a life-threatening situation, you can push the Hush button on the app and the smoke alarm will silence. However, if the smoke is too dense, the app Hush feature will not be enabled. This function only works if your mobile device and the alarm are connected to the same Wi-Fi network.