HANDLING OF RADIOISOTOPES WITH ANIMALS AND PLANTS 121 



are hard to keep clean; however, blowers spread dust, so that the choice 

 is a difficult one. 



Hoods. The purpose of the hood is to prevent contamination — such 

 as volatile compounds, spray, or dust — from escaping into the laboratory. 

 At low levels of the nonhazardous radioisotopes, work may be done on the 

 open bench if it is known that no air-borne contamination is being pro- 

 duced. Under slightly more hazardous conditions the ordinary chemical 

 fume hood may suffice, although tests have shown that it is usually ineffi- 

 cient in preventing the spread of fumes into the laboratory. For general 

 purposes, and in order to anticipate future work, it is desirable, if econom- 

 ically possible, to install a radiochemical fume hood, which is now available 

 commercially. Figure 4-5 presents a schematic diagram of a radiochem- 

 ical fume hood with mention of special features (3). If necessary to 



1 I I Sectional view 



ABODE 

 Fig. 4-5. Radiochemical fume hood. Special features: A, the hood should be resistant 

 to heat and chemical action and may be made of stainless steel or of less expensive 

 material such as Masonite, Transite, or fiirniture steel covered with the proper paint. 

 B, the interior of the hood may be given a final coating of washable, strippal)le paint, 

 which may be peeled off and replaced with a fresh coat if it becomes badly con- 

 taminated. C, a layer of replaceable absorbent paper with waterproof backing may be 

 used to cover the working surface of the hood; trays, preferably of stainless steel, 

 may be used for additional spillage protection. D, for proper fume control, all 

 operations should be performed beyond a safety line painted 8 in. inside the face of the 



