Global Congress on Process Safety, at the American Institute of Chemical Engineers Spring National Meeting, every spring in March or April. Unfortunately this just occurred a few weeks ago in New Orleans. This consists of the Center for Chemical Process Safety Annual Conference, the Loss Prevention Symposium, and the Process Plant Safety Symposium,
and normally draws several hundred people, good program and a great networking opportunity. (Note that CCPS is sponsoring its first ever local conference in South America, the last week of May in Buenos Aires).

Institution of Chemical Engineers (IChemE), United Kingdom, annual Hazards conference, normally in spring (it was April 14-27 this year, in Manchester)

Mary Kay O'Connor annual symposium at Texas A&M University, normally in
October.

There are also a number of "Responsible Care" type conferences held in
various places around the world by regional chemical industry groups.