They are fire alarm pull stations. They never actually activate an alarm or do anything else relevant to gameplay, but they relate to a number of achievements. Here are their descriptions as given in Steam:
- Fire Alarmist: Pull one fire alarm
- Expert Fire Alarmist: Pull enough fire alarms
- Fire Safety Achieved: Pull all the fire alarms
If you pull all the alarms (completing the Fire Safety Achieved achievement), then there is another bonus effect:
The main menu screen will have an option with a fire alarm icon, and if you choose it, a sprinkler animation will play in the background.
Other achievements and secret-finding can also add features to the main menu scene.
I believe the alarm stations in the “Clone” chapter which do not function normally do not count for the achievement, but I don't have proof.
If you're trying for the achievements, make sure to always turn around when you pass through a doorway to see if there's one on the wall behind you.
Related: the fire extinguishers, often found next to the fire alarm stations, have a set of achievements for emptying them (clicking them until they wheeze) and if you empty all of them,
Clicking any fire extinguisher in-game will cause it to shoot fire instead of white clouds.