Effect of Lack of Gravity on Airborne Infection During Space Flight

In the absence of gravity during flight in space, particles with high settling velocities on earth (20μ in diameter and larger) will remain suspended in the air of a spacecraft. If such particles are contaminated with infectious agents, they will present a potentially large source of airborne infection. Particles with small settling velocities which tend to remain suspended on earth will also remain suspended in space, and thus introduce no new infectious hazard into space flight. Nasal retention under gravity of nearly all particles 20μ in diameter and larger will be similar in the absence of gravity, unless the efficiency is reduced by overloading. Pulmonary retention of small particles (6μ in diameter and smaller), which on earth penetrate to the lungs in substantial percentages, will be reduced by two thirds in the absence of gravity, thus affording some protection to the lungs of travelers in space from airborne infection.