Where theres smoke theres fire? a strange Fire Investigation

Before my cancer battle I took care of a very large school districts alarms in the North Hills of Pittsburgh in an upper income area.
They had just opened a new middle school when I get called to reset the fire alarm and remove items in the computer lab after the sprinklers popped I get on site and get things secured and then in talking with the superintendent he asks me if I could help determine if there was a fire where it was and why the sprinkler heads went off.
I start by talking to the custodian a Volunteer firefighter who tells me he was sure he saw smoke in the hall way outside the computer lab but when he got there after hearing the alarms and starting down the hall the sprinklers went off and the smoke disappeared.By time trucks arrived. Ok but there is no smell of smoke was it electronic etc but what set the heads off not just smoke it takes165 degrees of heat and looking at the heads all 6 had there links melted. Things where just not adding up.
I then get up in the ceiling and notice everything is wet. Ok what is going on the pipes are also very warm. I then ask the custodian could that have been steam you saw which look like smoke and where any workmen in the school today and the light bulbs all start going on in all the school peoples head . Yes the HVAC guys where there and turned on the new central humidifier next to the computer room on today. We next opened up the ceiling above the humidifier and had our answer the fill valves stuck causing an overflow of water allowing the steam to build up inside the ceiling heating the pipes to the pint the sprinkler heads popped and it was steam that looked like smoke. The poor owner of the HVAC company showed up pale as a ghost and looking sick because tens of thousands in computers and data wiring where damaged and looked like he was on the hook for it. A mechanical engineer /fire investigator came the next day and came to the same conclusion I did the humidifier did the deed. the HVAC contractors insurance took care of everything and had the room back up and operating in short time.
Because I had photographed everything showing the steam and other marks before everything dried up it helped with the investigation. So this was definitely a strange type of Fire that was not.