Charging MacBook Air with a fast charger from usb-c
It shouldn't damage anything, but it might not be powerful enough to keep up.
The Macbook Air charger is 30w, which is about 6A.
Amps are &quot;pulled&quot; by the computer rather than &quot;pushed&quot; by the power supply [which is the opposite to voltage; this is why voltage has to match but amperage doesn't] however, your charger will be incapable of supplying all the Mac is asking.
This will just make charging slower. If you're lucky, it might just keep up, otherwise the battery might still lose charge slowly while the Mac is in use, even with the charger connected.