HANDLING OF RADIOISOTOPES WITH ANIMALS AND PLANTS 115 



tories, and the discussion is predicated on this i)asis. Certain features 

 are generally appHcable: The rooms of a radioisotope unit should be 

 grouped together to minimize the spreading of radioactivity to other areas 

 not involved in the work. Locating the laboratory on the top floor offers 

 the practical advantage of requiring short exhaust ducts leading from the 

 fume hoods to the roof. The laboratories should not be located in the 

 vicinity of X-ray machines, radium sources, or accelerators which may 

 interfere with the counting procedures. Separate areas and separate 

 facilities should be provided for high- and low-activity work to reduce the 

 possibilities of cross-contamination. If all the work is relatively low- 

 level, these various areas may be accommodated in the same room. The 

 counting area, especially, should be isolated if possible. 



The flow of ventilating air in the radioisotope unit should be from areas 

 of low activity to areas of high activity. This pattern will help prevent 

 the spread of radioactivity to the counting rooms or offices in the event 

 of accidental spills. The air in radioactivity rooms should not be recir- 

 culated. Since fume hoods remove considerable air, it is generally not 

 economical or essential to air-condition laboratory rooms containing 

 hoods. Fume hoods will also place a drain on the heating system. 



It is essential that all surfaces be accessible and cleanable so that radio- 

 active material spilled or deposited gradually over a period of time can be 

 removed without difficulty. The proper choice of surface materials, as 

 discussed later, is of prime importance. 



Typical Floor Plans. It is convenient to discuss the laboratory layout 

 in terms of areas set aside for specific purposes, which may or may not 

 reciuire separate rooms depending upon the magnitude of the experimental 

 work. 



The hot laboratory is used primarily for unloading the radioisotopes and 

 preparing the dilutions necessary for radiochemistry or for administration 

 to the biological system. It should be located near the isotope-storage 

 room, which may be used for storing both isotope shipments and radio- 

 active wastes. Likewise the hot laboratory should be located near the 

 injection area in which the radioisotopes are administered to animals. 

 There is often the likelihood of spillage in this area. The hot animal or 

 plant room is used to house biological specimens that have received radio- 

 activity. The medium-level laboratory is used for dissection of active bio- 

 logical material, ashing procedures, and radiochemical operations at 

 intermediate levels. At this stage care must be taken to avoid the cross- 

 contamination of samples, which will lead to counting errors. As the 

 name implies, the low-level laboratory will be used for operations in which 

 the materials have radioactivity at about the counting level. The 

 counting room is used for the (juantitative measurements of radioactivity 

 in samples, and in this area stray radiation or radioactive contamination 



