Carbon monoxide (monóxido de carbono) is a colorless, odorless gas produced when fuels burn incompletely (gas, wood, petrol, diesel, generators). It binds to blood and reduces oxygen delivery, causing headache, dizziness, nausea and can be fatal; if you suspect exposure, get fresh air immediately, call emergency services (112) and seek medical attention. For home safety, install battery-backed CO detectors and have heating appliances and chimneys inspected annually.