Yellow Admin Review is usually TAL (Technology Alert List) check. This kind of makes sense with your Chemical background. This is usually faster check compared to other types (like name-check). This used to take 21 days, you are around the same timeframe.
Originally Posted by statuslaw
I had my h1-b interview in Toronto on January 4, 2008 and got 221g yellow for administrative review. I called DOS one week ago for processing status and was told that name check is on pending. I called DOS today and was told that security check is on pending. Could you please let me know usually how many checks the DOS will do? How long the security will be done?