Actually, my primary kit is the 96 hour kit in the back of my truck. I don't have a dedicated BOB simply because I see no situation here where I'd abandon the truck. It's either in the garage, we're on the road or at work.

The events I need to worry about here are wildfires and earthquakes (SOCAL). Wildfires are not a surprise and for me there will be days available for an orderly evacuation. If a serious earthquake strikes, it will most likely hit areas around me but not where I live directly. The major faults are a good distance away and I expect the house to remain intact when San Andreas drops the other foot. LA and SF may take a big hit, but I'm off to the side of the major faults, not directly over them. In the very unlikely situation that I'm at work and the roads became impassable from the earthquake, I should have time to decide whether to wait it out and stay with the truck, or leave it parked and take the kit necessary to walk home. I won't know what BOB I'll need until the situation exists; hence I keep a comprehensive 96 hour kit near me from which to draw.

If your chemical spill forced me to abandon the truck and run, I'd consider the BOB detrimental to my well being -- carrying it would slow me down. Hopefully I'll be wearing my cross-trainers.