What is one of the most dangerous gases known?

Not carbon monoxide - which although lethal in small quantities, gives itself away by inducing serious headaches and dizziness. Not sulphur dioxide, which is evident from its \\$quot; rotten eggs\\$quot; smell. Ditto hydrogen cyanide, with its characteristic bitter almonds odour. No - common or garden NITROGEN! Harmless in the atmosphere, where it constitutes 78% of the air we breathe, it is deadly in pure form because it is odourless and produces NO gag reflex when inhaled. That is why, over the years, it has produced a significant number of fatalities, accounting for deaths in construction, petrochemical and other industries. Since it gives no warning of its presence and displaces oxygen in the lungs when inhaled, it can produce instant asphyxiation and death. And, for those of a criminal persuasion, it is impossible to detect in a postmortem.....