Sensor activating alarm?

Out kitchen sensor has started setting the alarm off, we've checked the room and there's been no one in and cleaned all around in case of spiders.
Could the sensor be faulty and if so:
Are there different types of sensors for the various alarms or are they universal?
Will I be able to change it myself or would it be best to get a professional to do it?
If the latter what sort of tradesman would carry out this type of work?