Chemical agents are poisonous vapors, aerosols, liquids and solids that have toxic effects on people, animals or plants. They can be released by bombs or sprayed from aircraft, boats and vehicles. They can be used as a liquid to create a hazard to people and the environment. Some chemical agents may be odorless and tasteless.
DURING A CHEMICAL EMERGENCY
Listen to local TV or radio for instructions on whether to evacuate or stay where you are. Your life could depend on it.
Local officials will tell you:
The type of health hazard.
The affected area.
How to protect yourself.
Evacuation routes, if necessary.
Type and location of medical facilities.
The phone numbers to call if you need extra help.
When officials say it is safe, open all doors and windows and turn on the air conditioning and ventilation systems to flush out any chemicals.
Remember: a person or thing that has been exposed to a hazardous chemical might be contaminated and could contaminate others. Follow decontamination instructions from local officials.
If you are outside during an incident, stay upstream, uphill and upwind. Gases and mists are generally heavier than air and hazardous materials can quickly be transported by water and wind. In general, try to go at least one-half mile (10 city blocks) from the danger area. However, for many incidents, you will need to go much farther.
If you are in a motor vehicle, stop and find shelter in a permanent building if possible. If you must remain in your vehicle, keep the windows and vents closed and shut off the air conditioner and heater.
Find more information here: https://www.ready.gov/chemical or http://www.vaemergency.gov/prepare-recover/threat/chemical-hazmat/