<prompt> The gas which produces systemic toxicity without causing local irritation is:AmmoniumCarbon monoxideHydrocyanic acidSulfur dioxide  <response>: B i.e. Carbon Monoxide Carbon Monoxide Poisoning CO is a colourless, tasteless, non irritant gasQ which is produced due to incomplete combustion of carbon. CO poisoning is defined as 15 carboxyhemoglobinQ in blood normal 1.5 in nonsmokers, 10 in smokers. Diagnosis is made by cooximetric measurements of blood not by pulse oxymeter. CO has 200 - 300 times the affinity of 02 for hemoglobin. It decreases the affinity of 02 and shifts hemoglobin dissociation curve to right. -Toxicity may be due to smoke inhalation or by degradation of desflurane by CO2 absorbent Lower levels produce systemic toxicity because of binding with cytochrome-c myoglobin and higher levels produce toxicity due to binding with Hemoglobin leading to tissue hypoxia. 