For Ploom S it depends on which heating mode you choose.

Standard mode - 20 seconds
If you want to start your session up quickly, insert an EVO tobacco stick, then press and hold the button until you feel one vibration. Your Ploom should heat up in around 20 seconds. 

Intense mode - 50 seconds
If you want an intense taste and aroma experience, insert a tobacco stick, then press and hold the button until you feel two vibrations. In Intense mode, Ploom will heat up in around 50 seconds. 

In both heating modes, you'll be able to check when your Ploom's ready using the LED lights. Once all the lights are lit up and Ploom vibrates again, it's ready to go.