Each box contains two of the overnight traps. The First Response Bed Bug Monitor is designed to help you detect bed bug infestations at home or while traveling. Just set a trap up before you go to bed, check the trap in the morning. The trap is effective for 24 hours.Bed bugs will be attracted to the heat and the lure, and get caught in the sticky pad. Against the plain white background, they'll be easily visible for confirmation that there are bed bugs present in the room.