Follow up on Litho Odor on Saturday, 10/20/07

Mary Tang mtang at
Tue Oct 23 13:04:58 PDT 2007

Hi everyone --

You may have seen Aaron Gibby's note on Saturday calling for an 
evacuation of litho due to a strong smell in that area of the lab.

The odor was determined to be due to a labmember's use of the headway 
bench -- a previous user apparently left a lot of stuff and the 
subsequent user tried to work around it, and so was likely not working 
fully under the ventilated area (remember, behind the red line!)  This 
labmember and his lab mate, however, could not smell the odor, although 
others did.

So, the moral of the story:

1.  Clean up after yourself.  This is not only courteous, but a good 
safety practice!
2.  Before working at a station, make sure it is clean and set up so 
that you can work safely!
3.  It's too easy to get used to a smell --  Don't rely on your nose; 
rely on good lab practices!

And please contact your favorite staff member if there are any concerns 
or questions.

(By the way, for those who may be interested, the chemicals causing the 
odor are: butyl acetate; 4-butyrolactone; and 1-methoxy-2-propanol 
acetate.  The OSHA PEL limit (exposure limit over 8 hours) for butyl 
acetate is 150 ppm (for comparison, PEL for isopropanol is 400 ppm.)  No 
PEL limits are established for the other chemicals, but none are 
identified as carcinogens.  These chemicals, in fact, are considered 
industry standard "safe" solvents for photolithography and are 
components in most of our standard resists and removers.  However, we 
all should make every effort to avoid exposing ourselves and others in 
the lab.)

Finally, we want to commend Aaron for doing exactly the right thing -- 
any time you feel safety is compromised, ACT! 

Thanks for your attention --

Your SNF Staff

Mary X. Tang, Ph.D.
Stanford Nanofabrication Facility
CIS Room 136, Mail Code 4070
Stanford, CA  94305
mtang at

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