It would force the rodent out and seal any openings the rat used.
I was away from home for three days on business. I still had four more days before we wrapped things up. After the fourth day, my wife called me with panic in her voice. When I asked her what was wrong, she told me that she had heard some strange noises in the house at night and she suspected that the noise was coming from the HVAC duct. Our house has a gas furnace and with that comes ductwork to ensure that the whole home heating system caterers for every space. Our home also has a gas fireplace which we rarely use. When I confirmed her fears that it was probably a rat, I could tell her panic went a notch higher. My wife grew up in a place where finding bear paw prints on your drive was a common occurrence. That woman could even face any big animal you can think of, but a rat is where she drew the line. I found it hilarious that she was terrified of rodents. I asked her to call the heating provider so that an HVAC repairman could conduct duct cleaning. It would force the rodent out and seal any openings the rat used. I made the call to the heating corp myself since we also needed furnace/heater tune-up, and the serviceman could wash the washable filter while he was at it. We always kept the boiler installation running efficiently with regular maintenance as an energy-saving help mechanism that we had learned over the years through home services professionals. That night, when I called my wife, she was happy to inform me that the rat must have fled because the noise had disappeared.