If you need to stay for long at Chennai Central: Luggage scanners available at Gate no.3. Scan it and get it sealed there and cloak rooms are available at side of pf.no 7. You will find staircase at side of pf.no 4 exit gate. Go up, right is AC waiting hall and left is Non-AC. Good facilities both sides. Washrooms are also available inside and below in front of staircase.