I was actually going to make a similar post tonight. My little guy is extremely afraid of the smoke detector. We have one that is hard wired in. (it was here when we bought the house) There is no way to remove the battery when cooking. Unfortunately Italian sausage sets it off. As soon as I turned the hood fan on over the over tonight he freaked out and ran to look up at the smoke detector. He was shaking by then and jumped in my lap. It wound up going off and he was shaking so bad I thought his fur was going to fall off. I noticed the panting too.
Once in a while he will be scared and bark at something stupid, but the smoke detector is the only thing that completely terrifies him.
Our older dog is terrified of fireworks and lightening. She hides if she sees the flashes or even hears thunder.
Poor Bella, I hate to see them shaking like that.
