I found this latest Letter of Interpretation regarding PSM Battery Limits an interesting read. The scenario is VERY COMMON and I am so glad OSHA wrote this letter! OSHA reminds us that cylinders stored in the same fire area (e.g. a fire has no passive control(s) to prevent its spread) that ALL of the cylinders that could be impacted by the same fire MUST BE AGGREGATED to determine if the threshold has been exceeded. NOTE: the person asking the question appears to be wanting to lay claim that each individual cylinder (DOT 3AA-2400) will be adequate “separation”. This letter hits the following key topics: