We usually set the fan speed to keep the temperature rise of the air passing through the system between roughly 40F-65F depending on the age and efficiency of your system. So, return air temperature may be 70F which means that the supply air measured in the furnace would be 110F to 135F.
exists and is an alternate of . Carbon dioxide is denser than air. The density of carbon dioxide is 1,977 g/L at 0 0C and standard pressure. The density of air (the so called International Standard Atmosphere) is 1,225 g/L. Carbon dioxide is denser than air. <br /> The density of carbon dioxide is 1,977 g/L at 0 0C and standard pressure. <br /> The density of air (the so called International Standard Atmosphere) is 1,225 g/L.
So any gas with a MW less than 29 will be lighter than air. That, by the way, includes nitrogen! Methane has a MW of 16; helium is 4; hydrogen is 2. I can't think of any other compound or element that's a gas at STP that has a MW less than 29. Afterthought: OK, neon has a molecular weight of 20, which is lighter than air. Ammonia (gas at room temp) has a MW of 17.