Which type of chemical agent when released can cause casualties for more then 24 hours to several days or weeks?

Persistent chemical agents, such as certain nerve agents and blister agents, can cause casualties for extended periods, from 24 hours to several weeks. These agents remain hazardous in the environment due to their stability and ability to contaminate surfaces and materials. Examples include agents like VX and mustard gas, which can linger and pose risks long after their initial release. Their prolonged effects make them particularly dangerous in warfare or terrorist scenariOS.