Construction began in 1965, and was completed in 1972. BIOS-3 consisted of a 315-cubic-metre (11,124 cubic feet) habitat suitable for up to three persons. It is divided into 4 compartments — one of which is a crew area. Initially one other compartment was an algal cultivator, and the other two 'phytrons' for growing wheat or vegetables. Later the algal cultivator was converted into a third phytron. A level of light comparable to sunlight was supplied in each of the 4 compartments by twenty 6 kW xenon lamps, cooled by water jackets. The facility used 400 kW of electricity, supplied by a nearby hydroelectric power station.
Chlorella algae were used to recycle air breathed by humans, absorbing carbon dioxide and replenishing it with oxygen through photosynthesis. The algae were cultivated in stacked tanks under artificial light. To achieve a balance of oxygen and carbon dioxide, one human needed 8 square metres (about 86 sq ft) of exposed Chlorella. Air was purified of more complex organic compounds by heating to 600°C (1,112°F) in the presence of a catalyst. Water and nutrients were stored in advance and were also recycled. By 1968, system efficiency had reached 85 percent by recycling water. Dried meat was imported into the facility, and urine and feces were generally dried and stored, rather than being recycled.
BIOS-3 facilities were used to conduct 10 manned closure experiments with a one to three man crew. The longest experiment with a three man crew lasted 180 days (in 1972-1973). The facilities were used at least until 1984, and are apparently still available for experiments (as of 2004).