The use of canaries as a means of warning in coal mines for more than a century was suggested by two Danish businessmen. Canairi is an air quality monitor that analyzes the levels of CO2 (carbon dioxide) in a home or indoors, and alerts people when they need to ventilate the room.
As its name indicates, this device uses a canary that ‘dies’ when carbon dioxide levels exceed 1000 ppm (parts per million).