What if I can't make it to a building?
If you can get to your car, go there. Turn off the ventilation system, close your windows and vents, and tune your radio to a local station.
If you are driving, try to avoid driving through a chemical cloud. If you are in a chemical cloud, be aware that your car may stall. Try to drive crosswind. If your car stalls or was not running when enveloped by the cloud, do not try to start it unless told to do so by a public announcement on the radio.
If you are outside and not close to a building, try to move crosswind. The vapors may drift downwind for miles and--unless there is no wind at all--you will not be able to outrun them. Going perpendicular to the wind and away from the center of the cloud will get you to a less harmful atmosphere more quickly.