Smoke detectors going off and killing my sanity

I bought a place around three years ago, and a few months after moving in, multiple smoke detectors started going off when there was no smoke or fire. I replaced them, but the new ones had the same problem. I replaced them again, with another brand, same problem. Called a local HVAC place I've used before & trust, they replaced them a third time and did some inspection to see if they could figure it out. They found nothing.

The alarms still go off at random. They go off at all times of the year. They go off at all times of day. There are certain areas of the house where they go off more frequently, but that's the only pattern I can discern. They went off again this morning, twice. The last time was around three weeks ago, at 4am; the prior time was a week before, around midnight.

Home was built in 2000, all the alarms are hardwired with battery backup. I have central air with a gas furnace. Furnace or AC being on or off doesn't seem to affect anything.

The ones that have a voice specifically say there's a fire. I've personally installed Kidde and First Alert brands, I believe the ones in here when I bought it were First Alert, and I replaced them with Kidde, then replaced those with First Alerts. These were purchased from Home Depot. I'm not sure what the HVAC company installed, but that's what I have now.

I've never experienced this or even heard of someone with this problem. I've spent hundreds trying to fix it with no results. It's killing my sanity. What do I do to fix this?