Fire extinguishing agents are not equal in the safety they provide for occupants. Reviewing the permitted limit for humans and the design concentration gives the best guide to an agent’s safety margin. The NOAEL (No Observed Adverse Effect Level) is the internationally established limit for the various extinguishing agents. The design concentration is the amount of extinguishing agent required to extinguish the fire safely. The margin of safety for humans arises from the relative difference between the design concentration and the specific NOAEL. As the chart shows, Novec 1230 offers, by far, the highest human safety margin.