MEMORANDUM 
TO 
FROM 
SUBJECT : 
DEPARTMENT OF HEALTH, EDUCATION, AND WELFARE 
PUBLIC HEALTH SERVICE' 
NATIONAL INSTITUTES Of HEALTH 
: Director, NIH 
date: December 9, 1977 
D1 rector 
Office of Research Safety 
Exhaust air treatment for P-4 facilities. 
Please note on page 1 1-29 of the proposed revised Recombinant DNA 
Guidelines, It states in paragraph 12 that "the exhaust air from the 
facility shall be filtered by HEPA filters..." Since there are other 
methods of fabricating filters which will achieve the required treatment 
objective, I would like to propose that we add the phrase "or equal" 
after "HEPA filters." This will allow those institutions that have 
in the past fabricated their own filters to meet the intent of these 
Guidelines; for example, the Microbiological Research Estate at 
Porton, England have over the years constructed their own filters 
out of fiberglass mat material. These filters are then tested against 
the same efficiency standards employed in the certification of "HEPA 
filters." Also the exhaust air treatment at the Fort Detrick 
facilities have relied on on-site fabrication of fiberglass filters. 
This proposed change does not alter the intent of paragraph 12. It 
does, however, recognize commonly accepted approaches used In the 
treatment of exhaust air from maximum security containment facilities. 
u) $cuJUuS /fi'f' 
W. Emmett Barkley, Ph.D. 
km 
[Appendix A — 106] 
