General advice on actions to be taken during these type of incidents:
Stay indoors until you are advised to leave by the Emergency Services. Bring pets indoors.
Close all doors and windows and block obvious vents (remember to unblock before switching equipment on again).
Tune into local radio and/or television and listen for local announcements.
Switch off air conditioning, ventilation units and fans.
Extinguish all naked flames.
Be prepared you may need to be evacuated, get an overnight bag ready.
Keep telephone calls to a minimum to avoid overloading the system.
Do not collect children from school unless instructed to do so as they will be looked after