Strep throat Strep throat is a throat infection causing symptoms including a red sore throat with white patches. Hay fever Hay fever, an allergic reaction to outdoor pollens and molds, causes nasal congestion, itchy eyes, and more.
Air Density is the mass per unit volume of the air. For example, the standard air density at sea level is 1.225 kg/m 3 (0.076474 pounds/ft 3). Relative Density is the ratio of the actual air density to the standard sea level density, expressed as a percentage.
More accurately, nitrogen, which is a constituent gas of air, is less dense than air, not lighter.   The density of air at standard temperature and pressure is 1.292 kg/m3. The density of nitrogen is 1.251 kg/m3. Shelly McFarland Faleska.