10 
the door to each laboratory room sometimes is left open and sometimes is 
kept closed, and because the airflow into ventilated cabinets may be inter- 
mittent. The latter condition has caused some installations to operate the 
blowers of ventilated cabinets continuously as part of the building venti- 
lation system. Of course, the air balance then requires adjustment whenever 
a ventilated cabinet is added or removed. 
III. THE DETRICK EXPERIENCE 
Fort Detrick was activated on 10 April 1943, and an operational safety 
officer for the pilot plant was appointed within the first month. By 
September 1943 a strong safety organization was organized and staffed 
principally by physicians and bacteriologists, most of whom were in military 
service. Formal written safety regulations were issued and well received by 
the laboratory personnel. However, the protective cabinets characteristic 
of P3 and P4 containment systems were absent. The years 1944 through 1969 
can be divided into three time periods, based upon the gradually increasing 
use of Class I ventilated cabinets and gastight Class III systems, and the 
development of effective vaccines for anthrax, tularemia, and Venezuelan 
equine encephalitis. No infections were reported in 1943. 
1 . 1944-50 inclusive, with 147 infections 
Facilities . During this time, there were no major primary barriers 
such as ventilated cabinets and ventilated closed cages to supplement the 
usual laboratory benches, except in one building, which was devoted to the 
study of microbial aerosols and the aerosol challenge of animals. This 
Building 524 and its activities have been described in detail by Rosebury 
(53). The building had no protective ventilated cabinets, but the more 
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