Question

What are the components of clean, dry air?

Answer 1

Clean and dry air contains nearly the same components or constituents as the normal air present in the atmosphere but the water vapour and other gaseous and vaporous contaminants are excluded from the calculations.

Complete answer:
Air that surrounds and envelopes the earth’ surface is a mixture consisting of a multitude of gases, vapors, and aerosols that are present in different concentrations that keep changing with the location and the time of measurement.
The particular matter that is small enough in size and has high mobility gets suspended into the atmosphere with ease. Thus the composition of air is not only limited to the gases essential for our survival but also a number of gases, particulate matter and microorganisms that act as contaminants.
The atmosphere also gets affected by the humidity levels in a particular area. Water vapour (the gaseous form of water) is abundantly present in the atmosphere that mixes homogeneously with the other gases in all proportions.
Thus, clean and dry air is the part of air excluding the water vapour and other non-gaseous contaminants in it. The composition of this clean dry air can be written as follows:
$78.09\%$ Nitrogen: the most abundantly available element in the air is nitrogen that is mostly present as a diatomic gas. The strong triple bonds that bind the two nitrogen atoms together in a molecule are responsible for its inert nature at room temperatures.
$20.95\%$ Oxygen: The second most abundant gas and one of the most important gases required by the living organisms for their existence on the planet Earth.
$0.93\%$ Argon: An important inert gas.
$0.04\%$ Carbon dioxide: The gas useful in maintaining the carbon cycle.

Note:
Even though the air around seems to be a homogenous mixture of its components, the components can be segregated. The gaseous and vaporous contaminants can be minimized or removed with the help of thermal or adsorptive devices.