85 
facility is isolated from general traffic patterns of the building. Access 
to the facility is under strict control. Class III Biological Safety Cabin- 
ets are available within work areas of the facility. 
A P4 facility has engineering features which are designed to prevent 
the escape of microorganisms to the environment (Figure 5). These features 
include: (1) monolithic walls, floors, and ceilings in which all penetra- 
tions such as for air ducts, electrical conduits and utility pipes are 
sealed to assure the physical isolation of the work area and to facilitate 
housekeeping and space decontamination; (2) air locks through which supplies 
and materials can be safely brought into the facility; (3) contiguous cloth- 
ing change and shower rooms through which personnel enter into and exit from 
the facility; (4) double-door autoclaves to sterilize and safely remove 
wastes and othr materials from the facility; (5) a biowaste treatment sys- 
tem to sterilize liquid effluents if facility drains are installed; (6) 
a separate ventilation system which maintains 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 cen- 
tral vacuum utility system is not encouraged; if one is installed, each 
branch line leading to a laboratory is protected by a high-efficiency par- 
ticulate air filter. 
Figure 5 
Ctangi Hoorn 
P4 Laboratory Suite 
Secondary Barriers 
[ 226 ] 
