Carbon monoxide test kit that is more sensitive than electronic detectors， detecting as little as 50 ppm (parts per million) of the invisible and odorless gas， before it becomes dangerous to you and your family. The kit contains a badge and 2 yellow chemical sensor buttons that turn grey when in contact with carbon monoxide gas. The instant detectors are reusable and， once opened， each button will last up to 3 months (90 days). Blister pack.