As we have discussed, the latest revisions of the Globally Harmonized System of Classification and Labelling of Chemicals (GHS) has a new criterion for categorization of flammable gases. The GHS now has sub-categories of CAT 1 Flammable Gases: 1A and 1B. CAT 1B flammable gases have a fundamental burning velocity of less than 10 cm/s. Never have I dealt with burning velocities to establish a degree of hazard for a flammable gas or vapor, but in all fairness, 10 cm/sec is really SLOW. How slow?