What if somebody explodes a dirty bomb on the subway? What should I do?

Avoid Panic. A dirty bomb is a conventional explosive that is mixed with radioactive material. It could potentially lead to radioactive contamination in the surrounding area. It is not a weapon of mass destruction but can lead to widespread fear in the public. Exit the subway & follow directives of emergency personnel. For a dirty bomb - there will likely be a decontamination site and medical evaluation.