<prompt> All are chemical Asphyxiants, except?HeliumCarbon MonoxideCyanideCarbon disulphide  <response>: Asphyxiants 1 IRRITANTS: The gases injure the air passages or lungs or both, and produce inflammatory changes.smoke, tear gases, ammonia, formaldehyde, chlorine, phosgene, nitrogen dioxide, sulphur dioxide. 2 CHEMICAL ASPHYXIANTS :The examples are carbon monoxide, hydrogen sulphide, arsine, carbon disulphide, and cyanide. 3 SIMPLE ASPHYXIANTS : They are carbon dioxide, methane, helium, nitrogen and nitrous oxide. Symptoms appear when these gases exceed 20 to 30 of inspired air. 4 VOLATILE DRUGS: absorbed through blood and toxic to internal organs like liver, kidney and CNS. They are aliphatic hydrocarbons, halogenated hydrocarbons and aromatic hydrocarbons. 5 SYSTEMIC POISONS : These are insecticides, arsine, stibine. 