See if an HVAC person or someone from a local animal shelter or vet can help, someone experienced in rescuing. But definitely call and hvac person first, so they can find out where the cat is.
She can be right there with them...even if they have to cut a hole, which would scare the cat - at least she can be there right after, calling to him. With some nice food.
Hope someone else has some good ideas.
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