Fire alarm keeps going off

Hi, I just moved into a new house and the fire alarms keep going off. Its not just one but all of them at the same time. The first time it happened i totally paniced and moved all of my animals to the yard before checking the whole house for a fire. I found no fire and i smelled no natural gas. A neighbor came over and told me that this happens and to cahnge all of the batteries. So i did that but they are still going off every 12 hrs or so. Im slowly loosing my mind. I honestly dont know what to do. Do i call the fire department? Does anyone know what specialist im supposed to call for this? The house is 20 years old, so could it be rime to replace all of them? Idk, everything online is just confusing me. Any help would be appreciated