White Knight vented dryer leaking

[D4N1EL]

Hi,
I've came home from work tonight and my mrs has had the dryer on, when it finished i brought the pipe back in (was out the window). I noticed it was quite wet and never though more about it, until i noticed the floor around the dryer itself was also wet. How does a vented dryer work and why would it leak?

Thanks

 

[rocks1]

Condensation going back down the pipe. Or pipe blocked with fluff. Make sure the pipe is level on the floor not out if the window. Fluff gets trapped in the pipe and over heats and causes it to catch fire.