Skip to Main Content

Maryland's National Register Properties

Photo credit: U.S. Army, 06/2001
One-Million-Liter Test Sphere
Inventory No.: F-3-46
Other Name(s): Horton Test Sphere
Date Listed: 11/23/1977
Location: Doughten Drive within Fort Detrick, Frederick, Frederick County
Category: Structure
Period/Date of Construction: 1951
Description: The One-Million-Liter Test Sphere is a 40-foot diameter sphere which during most of its existence was enclosed in a 60-foot wooden framed, metal sheathed cube. The sphere is gas-tight, constructed of 1 1/2" mild steel, with a painted interior finish. It is a freon tight air processing system capable of maintaining temperature within the range of 55-90 degrees F, dry bulb, at relative humidities between 20 percent and saturation. Five access ports at the equator are fitted with biological safety cabinets for aerosol sample collection and whole body exposure of small animal species, up to and including monkeys; one access on equator for personnel entry when facility is decontaminated; one access port on equator with newly constructed biological safety cabinets for whole-body exposure of large animal species, such as sheep and goats; four exposure cubicles on equator for mask exposure of volunteers; one access at base of facility with biological safety cabinet for introduction of disseminating devices and large items of equipment. Significance: As far as is known, the one-million-liter test sphere is unique--the largest such facility in the world. The facility was employed from 1951 to 1970 for aerobiological studies of agents highly pathogenic to man and animals, investigating biological agent stability in aerosol as function of environment, respiratory dose response characteristics in man and animal, evaluation of experimental vaccines with respect to conferred immunity against respiratory disease, and evaluation of biological agent aerosol detection devices and large-volume air samplers.


Return to the National Register Search page