When you leave a freezer door ajar in your kitchen, what happens? The refrigerator beeps, right? This warning is a simple and effective signal to avoid a problem. Behavioral scientists might describe that “beep” as an auditory prompt. It’s a cue to help people extinguish an unwanted behavior. The MASH alarm works in a similar way. The device beeps after no motion is detected for three minutes at a hood when the sash has been left too far open.