National Institutes of Health 
Dr. Fredrickson 
9/21/78 
Page 6 
diameter (figure 4 item 5 and figure 11 item 6) should be re- 
duced to 3/4" since some Class II cabinets have exhaust 
velocities over 250 feet/minute. We believe these additions 
are necessary because we have seen equipment and procedures in 
the field which fail to conform to almost every specification 
that we have recommended. 
The above comments are submitted in the hope that their 
inclusion will advance both research and safety simultaneously. 
If there are any questions about any of our points or if further 
elaboration is desired, please contact the undersigned. 
Very truly yours 
MEDICAL REPAIR LABORATORIES INC. 
President 
RIG: fw 
Enel . 
[A-223] 
