How would I know if something in my chest was a false positive?
Best way is upload it here>>http://www.virustotal.com/, but if the file system shield detects it, it will throw it right back in the chest as soon as you try to pull it out, so this means you need to temporarily set an exclusion for it.
If you do not care to take it that far, Avast! is very fast about clearing up FPs, so just leave it in the chest and re-scan it after one or two new definition updates. You can also submit a file to Avast! as a FP directly from the chest by right-clicking.
You would start by giving information on the detection in the topic, file name, original location and malware name; is this from a known program you have had for a while, etc. ?
From that alone we can get an idea on what to do next.
You could also check the offending/suspect file at: VirusTotal - Multi engine on-line virus scanner and report the findings here, post the URL in the Address bar of the VT results page. You can’t do this with the file securely in the chest, you need to extract it to a temporary (not original) location first, see below.
Create a folder called Suspect in the [b]C:[/b] drive. Now exclude that folder in the File System Shield, Expert Settings, Exclusions, Add, type (or copy and paste) C:\Suspect*
That will stop the File System Shield scanning any file you put in that folder.
Thanks for the replys. To clarify , I don’t have (or at least don’t think I have) any files that I think may be false psotitives, I wouldn’t know how to begin to figure out if one was a FP or not.
I have seen a lot of talk about FP’s, and wonder how people figure out that they might have a false positive in the first place. I appologize if this a a little too basic of a question.
Since installing Avast! last week it has found more stuff than my last 2 AV/ Secrity Suites (AVG adn Kaspersky) combined ever found. Nneedless to say Im happy with the results so far.
lcw731
Don’t worry to much you’re in safe hands we us here on the Avast forum we have great people here to help out with all kind of problems, and if you have a major problem with Avast or a virus that cannot remove or your windows operating system you’ve have come to the right place 
You can also scan the file in the chest after next definition update and If the file is still marked as virus - delete It.
+1 Agree
I would recommend waiting much longer than a day before deletion, the file should remain in the chest for longer and do periodic scans in the chest
There is no rush to delete anything from the chest, a protected area where it can do no harm. Anything that you send to the chest you should leave there for a few weeks. If after that time you have suffered no adverse effects from moving these to the chest, scan them again (inside the chest) and if they are still detected as viruses, delete them.
+1 I strongly agree with DavidR comments it very important, well said DavdR ;).