awk 'BEGIN { clean=1 } /#c3284d#/ { clean=0 } /#\/c3284d#/ { clean=1 } { if (clean==1 && match($0,"#\/c3284d#") == 0) { print $0 } }' dirty-file > clean-file
$ cat <<'EOF' | awk 'BEGIN { clean=1 } /#c3284d#/ { clean=0 } /#\/c3284d#/ { clean=1 } { if (clean==1 && match($0,"#\/c3284d#") == 0) { print $0 } }'
> foo
> #c3284d#
> bar
> baz
> #/c3284d#
> quux
> EOF
foo
quux