Answer: Completely extinguish cigarettes every time.
Step-by-step explanation:
The full PSA is: ''CIGARETTES DON'T KNOW WHEN YOU ARE ASLEEP''.
The meaning behind this PSA is that some people fall asleep whilst still smoking so they do not put off the cigarettes completely.
They therefore let it fall off their hands which can lead to it igniting something and causing a fire which can lead to fatalities. Indeed, smoking is apparently the number one cause of preventable fire fatalities in the home.
It is therefore advisable that the smoker should always put off their cigarettes to ensure that it does not lead to any fires.