There are instructions for several different Apple portable and desktop keyboards online.
You can take apart and usually replace the key-cap, the hinge-clip, and silicone cup.
Generally there are three-pieces that work together including the 'keyface' or top part.
Because the MacBook Air sub-category of portable Mac has several different builds of
design and fabrication, instructions and subsequent replacement parts, will differ, too.
In order to use information such as this, requires identification of the one example of
(your) MacBook/Air (11-inch or 13-inch) and manufacture date, CPU, GPU, & etc.
A general guide to access & replace these parts, can vary somewhat; there is a video:
Free Video Installation Guide - Apple MacBook Key Installation
https://www.replacementlaptopkeys.com/laptop-key-installation-guide/
Various 'build year' models of MacBook Air, & display size, have different part numbers.
One of the parts beneath the key-face may have debris trapped between sections.
The information is free at this site; to identify the correct part(s) is important. I've gotten
fair results on closed topcase portable Macs, by using the information online to help me.
And the only access to try this, is beneath each key. Otherwise it's an extensive take-apart.
Generally to replace the keyboard itself is an extreme effort & major disassembly process.
There are four general areas, by date & model, of MacBook Air; these differ, details matter.
• Apple MacBook Air Replacement Keys | Keyboard Keys | Keypad Keys
https://www.replacementlaptopkeys.com/macbook-air/
Not knowing more about your Mac, and be able to check into that model; I'm at loss.
Perhaps you can use this site's database to locate part numbers; and look into them.
Certain years of MB/Air keyboards use different key-switch technologies; parts vary.
Perhaps to use the images of the four eras MacBook/Air model series, to access data
may be best; at least initially. (These are also click on, with series name beneath.)
Use images of the parts, within each section, to determine which model you have.
The site features official Apple parts; you simply need precise information now.
With some information, this would be far easier to investigate; and learn more.
Good luck & happy trails!🌞🎣