Technical Tip Tuesday… nitrogen is NOT heavier than air! In fact, pure Nitrogen gas is LIGHTER (~3% lighter) than the Oxygen and Argon (with the Nitrogen) that make up our atmosphere. It is perfectly mixed in the air. Hence the air we are breathing right now (assuming you’re on the surface of the earth) is 78% Nitrogen. Nitrogen and Oxygen (21%) are perfectly mixed in or atmosphere. If N was heavier, those of us walking on the surface of the earth would be dead from lack of oxygen and the space ships we launch would never make it into space as they would explode as soon as they entered into the oxygen-enriched atmosphere above us. So when we need to inert the headspace of a vessel of flammable liquids, NEVER assume that just a little bit of nitrogen will “sit on the surface of the flammable liquid”… we MUST inert the entire headspace to below the “Limiting Oxygen Concentration (LOC)” of the flammable vapors. This requires a detailed engineering design basis – not a SWAG (seriously wild ass guess)!