The risk of a catastrophic explosion of a damaged chemical tank Southern California has been eliminated following a close overnight inspection that confirmed a crack in the tank has relieved pressure and cooled the chemical. Officials said crews conducted tank temperature checks at night to reduce risks to firefighters, avoiding daytime operations when heat from the tank made conditions around it most dangerous. The overnight mission allowed crews to verify the crack and confirm temperatures were falling, Orange County Fire Authority division chief Craig Covey said Monday morning.