If the class has 300 students, there are 40/100*300 = <<40/100*300=120>>120 smoking students.
In a year, 70% of the smoking students are hospitalized from smoking-related complications, a total of 70/100*120 = <<70/100*120=84>>84 students.
The number of smoking students who've not been hospitalized from smoking-related complications is 120-84 = <<120-84=36>>36
#### 36