Many boats these days have gas stoves, BBQ, or even cabin heaters that run on propane or LP gas and it is very important to be able to detect even the smallest leak before it becomes a hazard. Most manufacturers recommend that you test their unit monthly or even weekly. Testing is easy if you have butane lighter (butane is a type of LP gas). Just press the gas without igniting the sparker, or blow out the flame, and hold the lighter near your detectors sensor. Note that some gas detectors have the sensor located away from the unit’s display, usually closer to the ground.
You should know where your gas detector sensor is and how to test it. It is also a great way to familiarize yourself with the sound your detector makes, so that if it does go off, you will recognize the source of the alarm right away.