Brian Whatcott wrote:
Nitrogen displaces oxygen, so you pass out without warning.

Keith Hughes wrote:
Nitrogen does not *displace* oxygen (O2 weighs more than N2). Excess
Nitrogen will reduce the partial pressure of oxygen.
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Once again, this is copied directly from the MSDS (Emphasis added):

Material Safety Data Sheet
Gaseous Nitrogen:

SIMPLE ASPHYXIANT
Section 3 : HAZARD IDENTIFICATION
Emergency Overview:
Nitrogen gas is colorless, odorless and non-flammable.
It is non-toxic. The primary health hazard is asphyxiation by
displacement of oxygen.

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