Building miniature greenhouses for experiments on the
International Space Station has led to the invention of a
device that can destroy Anthrax — a bacteria that can be
deadly when inhaled.

The Anthrax-killing air scrubber, called AiroCideTiO2
(titanium dioxide), is a tabletop-size metal box that bolts to
office ceilings or walls. Its fans draw in airborne spores
and airflow forces them through a maze of tubes. Inside,
hydroxyl radicals attack and kill pathogens. Most remaining
spores are destroyed by high-energy ultraviolet photons.

The technology to build the device emerged from another
product called Bio-KES, which today is used by grocers and
florists to remove ethylene and thus extend the life of
vegetables, fruits and flowers. Ethylene is a gas released by
the leaves of growing plants — but too much of it can build
up in an enclosed plant-growth chamber or produce storage

Too much ethylene causes plants to mature too quickly and
fruit to ripen prematurely; it even accelerates decay. This
hinders researchers’ efforts to harvest healthy plants grown
in space and would also be undesirable when space travelers
build larger space-based greenhouses for growing fresh food.

The research that led to the invention of Bio-KES started with
a crucial discovery made in the early 90s by scientists at the
Wisconsin Center for Space Automation and Robotics – a NASA
Commercial Space Center at the University of Wisconsin-
Madison. These scientists collaborated on the discovery with
Dr. Marc Anderson, a professor and chemist also at the

The research team found that ultra-thin layers of titanium
dioxide exposed to ultraviolet light converted ethylene into
carbon dioxide and water — substances that are good for
plants. Subsequently, they developed a coating technology that
applies titanium-dioxide layers to the surfaces of many

The Wisconsin Center for Space Automation and Robotics used
the titanium-dioxide coating technology to design an ethylene
scrubber. This first-generation ethylene scrubber was used
effectively inside a plant-growth unit, which grew potato
plants during a space shuttle mission in 1995. Over the years,
scientists refined the ethylene scrubber, and currently the
third-generation scrubber is being used successfully inside
for plant experiments on the International Space Station.

“Space-based greenhouses may seem to have little to do with
the war against terrorism,” said Mark Nall, director of the
Space Product Development Program at NASA’s Marshall Space
Flight Center in Huntsville, Ala. “Yet this invention shows
how commercial space research can benefit people on Earth in
unexpected ways.”

KES Science and Technology, Kennesaw, Ga., licensed the TiO2
coating technology from the University of Wisconsin, which
allowed them to develop the Bio-KES ethylene scrubber and the
Anthrax-killing scrubber for use on Earth. When the
ultraviolet light strikes the titanium-dioxide tubes inside
the devices, it creates positive and negative electrical
charges. These charges tear apart nearby water molecules and
produce hydroxyl radicals.

“This hydroxyl by-product disrupts organic molecules and is
thus deadly to dust mites, Anthrax and many other pathogens,”
said John Hayman, president of KES Science and Technology, the
company that manufactures the devices. “We put higher-powered
ultraviolet lamps in the Anthrax-killing device, so more
hydroxyl radicals are produced, giving it an extra kick.”

More information on space station experiments and science
operations is available at: