If a combination of chemical agents is used as a weapon to generate mass destruction amongst a group or civilization it is considered a chemical warfare weapon. Chemical warfare agents can release in liquid, gas, or aerosol. Additionally, though there are thousands of toxic substances known there are only a few that are considered as a chemical warfare agent. This is highly dependent on a variety of factors that make up the agent including; high toxicity, characteristics, rapid action, viz, and persistence.
The Chemical Weapons Convention of 1993 outlaws both production and stockpiling of any such weapon. However, chemical terrorism continues to pose a threat across the world today. After recent events in 2018, involving fourth-generation agents in the United Kingdom, the White House National Security Council assembled different agencies together to discuss how they could prepare for a fourth-generation agent incident. The agencies have compiled resources needed in case of such an emergency including EMS, HAZMAT, law enforcement, Occupational Safety and Health Administration, U.S. Department of Defense (DOD), and more. Additionally, the United States government has developed a Chemical Hazards Emergency Medical Management (CHEMM) resources to address the overall safety of first responders, hospital staff, and individuals involved in the chemical attack. There is no current manufacturing of or threats of such products in the United States today.