: Carbon monoxide, produced by gas heaters, charcoal stoves, coal mines etc. corubines with haemoglobin, producing carboxyhaemoglobin or COHb . At 50 ppm, CO converts 7.5% of haemoglobin into carboxy-haemoglobin within 8 hours. It impairs oxygen transport resulting in suffocation, giddiness, headache, decreased vision, cardiovascular malfunction and asphyxia.