The open perils policy is the counterpart to the named perils policy. In it, any peril NOT mentioned is covered by the policy.
Here's an example: let's say you got an open perils policy homeowner's insurance and it lists volcanoes eruptions and floods. If there was a fire or if a hurricane sent a tree through your window (and, why not, it provoked a fire afterward), your damages will be me covered and your house repaired by the insurance company. Now, if a volcano erupted and lava burned your house to the ground or a flood damaged the whole electrical circuit... sorry, no deal. You're on your own.
So, basically, if the insurance company cannot prove that whatever happened to your house was listed as an exclusion, they will have to afford the repair or replacement of it.
This is usually done in areas where it is just highly probable for specific damages to happen. So, you will most likely find open peril listing volcanoes on Hawaii than in Florida, because, what's the point?
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