83 
Figure 3 
P3 Laboratory 
Cabinets and an autoclave are available within the controlled laboratory 
area. The surfaces of walls, floors, bench tops, and ceilings are easily 
cleanable to facilitate housekeeping and space decontamination. 
Directional air flow is provided within the controlled laboratory area. 
The ventilation system is balanced to provide for an inflow of supply air 
from the access corridor into the laboratory. The general exhaust air from 
the laboratory is discharged outdoors and so dispersed to the atmosphere as 
to prevent reentry into the building. No recirculation of the exhaust air 
shall be permitted without appropriate treatment. 
No work in open vessels involving infectious hosts or vectors contain- 
ing recombinant DNA molecules requiring P3 physical containment is conducted 
on the open bench. All such procedures are confined to Biological Safety 
Cabinets . 
The following safe microbiological practices and laboratory techniques 
in addition to those identified for PI and P2 apply to all experiments re- 
quiring P3-level physical containment. Appropriate biohazard signs are 
posted at access points to the laboratory, and only persons specifically 
authorized by the principal investigator enter when these signs are posted. 
Normally, authorized persons are limited to those who work in the laboratory. 
[224] 
