52 
Figure V- 5 
r 
P* Laboratory Stile 
Second* y Bamers 
The secondary safeguards of the facility include: (1) monolithic 
walls, floors, and ceilings in which all penetrations, such as for air 
ducts, electrical conduits, and utility pipes, are sealed to ensure the 
physical isolation of the work area and to facilitate housekeeping and 
space decontamination; (2) air locks through which supplies and materials 
can be brought safely into the facility; (3) contiguous clothing -change 
and shower rooms through which personnel enter the facility and exit 
from it; (4) double -door autoclaves to sterilize and safely remove wastes 
and other materials from the facility; (5) a biowaste treatment system 
to sterilize liquid effluents; (6) a separate ventilation system that main- 
tains negative air pressures and directional air flow within the facility; 
and (7) a treatment system to decontaminate exhaust air before it is 
dispersed to the atmosphere. 
A measure of the degree of safety afforded by P4 containment is the 
fact that, in the past, such precautions were only applied in work with 
viruses that are extremely hazardous to laboratory personnel or that 
may cause serious epidemic disease. For example, these safeguards 
are recommended by the Center for Disease Control for work with the 
viruses of hemorrhagic fever, encephalitis, Lassa fever, and Marburg 
disease. Similarly, such maximum containment has been used in the 
study of the airborne transmission of pathogens, which involves the 
generation of highly concentrated aerosols. 
Further Information on Physical Containment . An extensive discus - 
sion of physical containment is given in Section VII-A-1 and -2. Further, 
Appendix J (Section V-E) contains information on current NIH activities 
in biohazard assessment, development of safer host-vector systems, 
and training. 
