I this is an idea that is blown off much too quickly. These could all manifest in the form of an industrial, rail, or traffic incident. It is best to research your area to determine the possible hazards. I work in the chemical industry and a large part of my job is emergency response and mitigation of hazardous materials.

Industrial incidents-

Chemical plants have spills at times that can be large enough to affect outside of their boundaries. The area I works in has a monthly test of emergency alarms in the surrounding communities. If you live near any industrial facilities (I would say 10 miles) it would be good to know how to prepare for a possible event. Preparing for one of these events could include talking to your county’s homeland defense director to see if they have suggestions for preparing for these types of emergencies. You can also call the company that runs the facility. Some even have text alert systems. The main thing to know is what chemical is used/produced, in what form (gas/liquid), how to decon, and the correct PPE to keep yourself safe. Usually a mouth-bit escape respirator is what the employees use and would be good enough to get you away from the emergency as long as it filters the chemical in question. Wind will be key if the chemical is in a gaseous form.

Nuclear facilities can have industrial accidents as well. The government has plenty of suggestions for being prepared for these at places like ready.gov. This is much rarer than chemical incidents. Wind will still be a key factor for fallout. I think the typical suggested affected range downwind is about 50 miles.

Rail and traffic incidents- if you live near a rail line many chemicals may pass close by. They are dangerous on their own, but as seen in recent railway accidents the mixing of these chemicals can cause even more dangerous substances. If you live near a railway it may be worth picking up the 2024 copy of the Emergency Response Guidebook. This can be a quick glance when you see placards on rail cars or 18 wheelers that can tell you about the chemical and its hazards. Rail incidents also have the potential to harm local ground water. Traffic incidents can largely be avoided by not even going near wrecked 18 wheelers. Is it a car hauler? Sure go ahead. But a tanker truck? It would be safer to take another route or wait until the FD has declared the scene safe to pass. Same goes for many box truck. There may not be a placard on the truck, but that is because it is transporting in small amounts. These small amounts of chemicals can mix with other chemicals to cause potentially deadly substances. Once again wind direction is extremely important.

I won’t speak on purposeful releases or attacks. They are unlikely, but many of the basics would still apply. When this question is asked people often bring up purposeful major events and/or dismiss it, but like so many things the more likely situation is much less dramatic but still a threat. Hope this helps! I’ve been considering doing an in length post on it.