What chemical warfare during the Vietnam War?

If you are asking about Agent Orange et al, you may be interested in checking these posts:

http://www.reddit.com/r/AskHistorians/comments/1lwucw/is_this_statement_true_about_the_vietnam_war/

http://www.reddit.com/r/AskHistorians/comments/1dqvkq/to_what_extent_did_the_us_military_understand_the/