Exclusion really isn't the way to go - Anything that you consider a false positive, shouldn't just be ignored (avira speak) or excluded from scans (avast), that is shooting the messenger rather than treating the problem.
Confirm by examination (virustotal) that it is indeed an FP, if so send the sample for analysis and correction of the detection signature plus inclusion in a signature update. This helps all avast users.
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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
C:\ 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.
