hood from the room. The vertical laminar flow hood 2 draws only 10-20 percent of the air used from the room. The 

 remainder of the air is recirculated through biological filters. A vertical laminar flow hood provides about the same 

 protection as a closed cabinet that does not have glove ports. Any air control system can give a false sense of security 

 if it is not selected carefully and checked continuously. The selection and use of air control systems are covered in 

 more detail in references (2, 4, 5). When working with Venezuelan equine encephalitis, Chlamydia agents, and other 

 hazardous agents we do all the work inside a vertical laminar flow hood in a laboratory under negative pressure. 



Movement of Personnel 



Extraneous persons should be discouraged from entering any laboratories where virus isolation procedures are 

 being carried out. If a hazardous or exotic virus is suspected, the supervisor should allow only essential personnel 

 into the laboratory. It may also be desirable to require all personnel to take a decontaminating shower before leaving 

 the laboratory. If a hazardous viral agent is being used on a routine basis as part of a test procedure, it may be 

 advisable to keep the laboratory closed at all times. Whenever possible, an avirulcnt or killed agent should be used in 

 place of a hazardous agent. The laboratory surfaces can be disinfected and the laboratory opened to other personnel 

 when low-risk agents are being used. Signs should be posted outside the laboratory describing the hazard and the 

 procedure for admittance. 



Movement of Equipment and Supplies 



All specimens, equipment and other material that may have been in contact with viral agents should be 

 disinfected or incinerated. Autoclaving is the ideal method of disinfection. For certain equipment and supplies, other 

 methods of sterilization may be used such as formaldehyde vapor (6), ethylene oxide or ultraviolet sterilization. The 

 sewage leaving the laboratory should be treated to kill pathogenic agents. It is not advisable to flush infected 

 material down drains even if sewage is treated. Due to aerosol production, garbage disposals are not recommended. 



Laboratory Clothing 



Personnel working in a diagnostic virology laboratory should be provided with at least laboratory coats and 

 preferably a complete set of clothing. When working with hazardous agents, laboratory clothing should be left 

 within the laboratory and autoclaved out. As a minimum precaution, laboratory coats should not be worn outside 

 the laboratory and other laboratory clothing covered with a different type of laboratory coat. Using a different 

 color of clothing within the laboratory helps prevent inadvertent use of laboratory clothing outside the laboratory. 



General Laboratory Procedures 



The following is a list of procedures which we use to help maintain biological security. Most of these are 

 dependent upon the laboratory worker so each individual should understand the basic principles and importance of 

 biological security. 



1. Wash hands frequently— especially between procedures or before eating, drinking and smoking. 



2. Disinfect table surface after working with each specimen. 



3. A minimum of reference material and supplies should be kept in viral isolation areas. 



4. Wash and disinfect floors as needed. 



5. Immediately clean all viral material that is spilled. 



6. Use tightly sealed containers for centrifuging. 



7. Do not eat or smoke in the same area and at the same time as viral material is being processed. 



8. Stock reagents, cleaning supplies, brooms, etc., should not be removed from the laboratory without 

 disinfection. 



9. Laboratories should be insect- and rodent-free. 



10. Pipettes should be plugged with cotton and there should be no mouth -pipetting. It is advisable to use 

 bulbs for all pipetting in a diagnostic virology laboratory. 



2 The Baker Company, Inc., 106 Granite Street, Biddeford, Maine 04005. 



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