Everyone knows there’s oxygen in our air – if there wasn’t oxygen in the air you’re breathing right now, reading this blog would be the least of your concerns. Most people know that oxygen, in fact, makes up about 20% of the earth’s atmosphere at sea level, and that almost all the rest is nitrogen. There’s an impressive list of other gases in the air we breathe, but what’s more impressive (to me, anyway) is the technology behind the instrumentation needed to measure some of these values:
We can consider, for practical purposes, that air is made up of five gases: nitrogen, oxygen, argon, carbon dioxide, and water vapor (more on that in a minute.) The other gases are so low in concentration that there is over 10 times as much carbon dioxide as all the others below it, combined.
About the water vapor: because it’s a variable, this table omits it, water vapor generally makes up 1-3% of atmospheric air, by volume, and can be as high as 5%. Which means that, even on a ‘dry’ day, it pushes argon out of the #3 slot.
There are numerous reasons why the volumetric concentrations of these gases are important. If oxygen level drops in the air we’re breathing, human activity is impaired. Exhaustion without physical exertion will occur at 12-15%. Your lips turn blue at 10%. Exposure to oxygen levels of 8% or below are fatal within minutes.
Likewise, too much of other gases can be bad. Carbon monoxide, for example, is a lethal poison. It’ll kill you at concentrations as low as 0.04%…about the normal amount of carbon dioxide in the atmosphere.
For the purposes of this blog, and how the makeup of our air is important to the function of EXAIR Intelligent Compressed Air Products, we’re going to stick with the top three: nitrogen, oxygen, and water vapor.
Any of our products are capable of discharging a fluid, but they’re specifically designed for use with compressed air – in basic grade school science terms, they convert the potential energy of air under compression into kinetic energy in such a way as to entrain a large amount of air from the surrounding environment. This is important to consider for a couple of reasons:
- Anything that’s in your compressed air supply is going to get on the part you’re blowing off with that Super Air Nozzle, the material you’re conveying with that Line Vac, or the electronics you’re cooling with that Cabinet Cooler System. That includes water…which can condense from the water vapor at several points along the way from your compressor’s intake, through its filtration and drying systems, to the discharge from the product itself.
- Sometimes, a user is interested in blowing a purge gas (commonly nitrogen or argon) – but unless it’s in a isolated environment (like a closed chamber) purged with the same gas, most of the developed flow will simply be room air.
Another consideration of air make up involves EXAIR Gen4 Static Eliminators. They work on the Corona discharge principle: a high voltage is applied to a sharp point, and any gas in the vicinity of that point is subject to ionization – loss or gain of electrons in their molecules’ outer valences, resulting in a charged particle. The charge is positive if they lose an electron, and negative if they gain one. Of the two gases that make up almost all of our air, oxygen has the lowest ionization energy in its outer valence, making it the easier of the two to ionize. You can certainly supply a Gen4 Static Eliminator with pure nitrogen if you wish, but the static dissipation rate may be hampered to a finite (although probably very small) degree.