20 
3. For the purposes of the following Conclusions , the Class I 
ventilated safety cabinet used at Fort Detrick is considered to be equivalent 
to the ventilated safety cabinets specified in P3 and P4 conditions. 
IV. CONCLUSIONS 
1. Class III gastight microbiological cabinet systems, which are neither 
required nor excluded by the definition of P4, can be operated without 
infection of the operators, in the very hazardous whole-body and head-only 
aerosol exposure of small animals and monkeys to USPHS Cotununi cable Disease 
Center Class 3 and 4 etiologic agents, under standardized somewhat regularly 
repetitive procedures, with stable, well -trained, wel 1 -disci pi ined personnel 
(Detrick Bldg. 1412, Aerobiology Unit, December 1959 - December 1969). 
2. When gastight cabinet systems are used for basic and applied research 
with Class 3 and 4 agents, in a changing variety of techniques, procedures, 
equipment, and experiments, there will be some laboratory infections, usually 
due to breaks in the attached rubber gloves, human exposure during entrance 
and exit of materials, leaks in the system, and human error. (Bldgs. 459-1412, 
during 1952 through 1969: Less than one infection every two years) 
3. When a gastight cabinet system and Class I cabinets are both used 
in aerosol studies with Class 3 and 4 agents, there will be an increased 
number of infections, in comparison to use of only a Class III system. 
(Bldg. 376 - 18 infections during 1953 through 1958, and only 2 thereafter, 
mostly due to the introduction of live tularemia vaccine in 1959 and live 
VEE vaccine in 1963, which ended infection with those two agents. In the 
entire period 1953 through 1969, there were 20 cases in 17 years, which is 
a good record.) 
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