82 
Figure 2 
Sink 
P2 Laboratory 
The following safe microbiological practices and laboratory techniques 
in addition to those identified for Pi apply to all experiments requiring 
P2-level physical containment. Access to the laboratory is controlled when 
handling potentially hazardous organisms requiring P2 containment, but not 
otherwise. During the controlled period, appropriate biohazard signs are 
posted at access points to the laboratory, and only authorized persons who 
have been advised of the potential biohazard enter when such signs are post- 
ed. The signs are removed upon completion of decontamination after the ha- 
zardous procedures. Experiments of less biohazard can be carried out con- 
currently in carefully demarcated areas of the same laboratory if necessary, 
given that adequate precautions are taken to avoid cross-contamination and 
no animals or plants are in the area. Mouth pipetting is prohibited; me- 
chanical pipetting devices are used. Specific precautions are required for 
those procedures that have a high potential for release of aerosols contain- 
ing potentially hazardous material — e.g., centrifugation should be carried 
out in airtight cups or rotors, and sonication and blending are similarly 
contained or carried out in appropriate enclosed biological safety cabinets. 
All potentially hazardous material is inactivated before it enters the 
drainage system. 
P3 Level (Moderate) . A laboratory suitable for experiments involving 
recombinant DNA molecules requiring physical containment at the P3 level 
has special engineering design features and physical containment equipment 
(Figure 3). The laboratory is separated from the general traffic patterns 
of the building. Access to the laboratory is controlled. Biological Safety 
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