Dust sets off fire alarms?

This is a picture of our space as of Thursday the 18th of Feb. Doesn't seem like much yet but the contractor had just started construction early that week. Funny story though, just earlier the same day I took this picture, I had come to the space at 9am for a standard food supplier meeting. Parked directly outside the space was a fire truck with its lights flashing. And in-front of the building was a large group of people I could only guess were employees from the offices above us. It goes without saying I was a little nervous, and the siren/beeping coming from inside our space wasn't relieving any stress. Thankfully when I got into the space I found out an abnormally large amount of dust in the air from all the cleaning was the cause of panic. Just want to also note our contractor was happily handing out free pens to all the firemen as they were exiting the space!

Lesson of the day: Dust can set off fire alarms, and if that happens, hand out free pens