11 
hazardous operations preparatory to aerosol challenge were done in a Reyniers 
germ-free chamber with arm length attached gloves. Animals were kept in 
ventilated closed cages with exhaust air passed to an oil-fired incinerator. 
Secondary barriers were present in a developmental stage in Building 524 and 
in most of the other laboratory buildings (restricted access; air locks; 
exit autoclaves; refuse incineration; exhaust air treatment that provided a 
negative air balance in the building; clothing change; exit showers). 
Infections, 1944-50 inclusive . There was a marked difference between 
the number of infections in Building 524 in which hazardous experiments were 
done with various infectious microbial aerosols inside containment equipment, 
and the number of infections in other buildings of reasonably comparable size 
in which basic research confined to a single microbial species was done on 
open bench tops. No experimental aerosols were generated in these other 
buildings. 
In Building 524, in the 6 months 21 March 1945 to shortly after the 
end of World War II, with intensive study of aerosols of P_. tularensis , 
B. suis , M. mallei , M. pseudoman ei , and psittacosis agent, there was only 
one infection, caused by a leaking frozen ampule of psittacosis agent handled 
on the open bench top. There were no ventilated cabinets in use at Fort 
Detrick at that time. The absence of ventilated safety cabinets to use in 
preparing test materials and in making examinations subsequent to aerosol iza- 
tions in the gastight steel chamber was a major safety weakness. Operations 
ceased late in 1945 and were resumed sometime in 1946. The subsequent record 
of only 5 cases of brucellosis in Building 524 during 1946-50 also was good, 
considering the obvious hazard associated with aerosol clouds in the chamber 
and adherence of the test microorganisms to the hair of experimental animals, 
mostly mice and hamsters. 
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