While a Avast scan is running will it slow down my computer?
Yes.
For me, scan slows my computer.
I have noticed a slight slow down. Not enough to be a bother.
It doesn’t impact my system at all, but I’m not running lots of other things in the background.
This really begs the question, why start an on-demand scan if you are going to be working on it at the time (especially if you have a lower spec system).
Your best option would be to schedule the scan so it happens at a time which is convenient to you, when you aren’t using it if you leave your system on at night, etc. Either that or do what I used to do before the scheduled scanning was available, start the scan and go and have a cup of tea.
That’s a good idea.