I have been catching up on my Chlorine posts these last several weeks and some have asked me how I know which chemical goes into which hazard class; specifically, why Chlorine is “only toxic” and not “highly toxic”. As I said in a few of my previous articles on safely managing Cl2, some of my businesses that had actual “highly toxic” materials went ahead and put Cl2 into that group for “good measure”, some even built their process as “lethal service”. We were already managing some actual HAZMATs that were by definition “highly toxic” so adding Cl2 to this group was not difficult or expensive. But for a facility that does not already have materials that have to be managed as “highly toxic”, doing so with Cl2 will require an extra effort and full support from management. Heck for that matter, by code, even Phosgene is only “toxic” but in the two businesses I worked for that had Phosgene, one managed it as a “highly toxic” and “lethal service”. Here is a nice cheat sheet of what the IFC considers “toxic” and “highly toxic” compressed gas for the proper application of the code: