February is Black History Month, and we would be remised if we did not share the stories of two innovative Black inventors, whose contributions changed the filtration industry forever.

Dr. Rufus Stokes – Inventor of the “Clean Air Machine,” an early concept of air purifiers.

Born and raised in Alabama, Dr. Rufus Stokes enlisted in the US Army right before graduating from high school. While in the army, Dr. Stokes attended a technical school where he was trained in auto mechanics. This training helped him find work in Missouri and Illinois after he was honorably discharged from the army. Dr. Stokes received the American Defense Service Medal, European-African-Middle Eastern Campaign Medal, and Good Conduct Medal.

While working at Sanitarium and Brule Inc., he became interested in air pollution and decided that he wanted to figure out different ways to purify breathing air. Dr. Stokes invented the “Clean Air Machine:” an air-purification device that reduced the gas and ash emissions of furnaces and power plant smokestack emissions in the 1960s.

This technology was his unique utilization of what he described as “the three Ts”:

• Temperature
• Time
• Turbulence

Dr. Stokes created a small domestic version and a larger mobile version of this air purification device to show its versatility. During that time, most air pollution control technologies were more cumbersome and less efficient, but the “Clean Air Machine” was not limited by design and configuration; its efficiency remained excellent regardless of industrial or residential applications.

Dr. Stokes’s “Clean Air Machine” improved the respiratory health of so many people and significantly reduced health risks to plants and animals. An additional benefit of his clean air machine was that it reduced industrial stack emissions which ultimately improved appearance and durability of buildings, cars, and objects exposed to outdoor pollution for lengthy periods of time. Dr. Stokes laid the groundwork for many scientists to contribute to clean air and the reduction of pollution.
Sadly, major companies denied smog emissions which caused disbelief in how efficient the “Clean Air Machine” was. Many people were not willing to invest in Dr. Stokes’ clean air machine, which prevented the widespread use of Dr. Stokes’s inventions.

However, his patent inspired many new inventions in air purification for both industrial and residential environments. In 1986, Dr. Stokes died of mesothelioma, an asbestos-related disease. Since his death, Dr. Stokes has been honored with inclusion in the United States Department of Energy’s (DOE) list of “Energy Pioneers” and acknowledged in the technology white paper “Quantum Parallel.”

Andrew F. Hilyer- Inventor of the Evaporators for Hot Air Registers which were the pre-cursor for humidifiers.

Andrew F. Hilyer was born a slave in Georgia in 1858. He left the South and eventually settled in Minneapolis, Minnesota.
While living as a free man in Minneapolis, he met and befriended wealthy families including the Pillsbury family of The Pillsbury Doughboy Company, who helped support his education. Hilyer became the first African American graduate from the University of Minnesota in 1882. He continued his education at Howard University’s Law School where he earned an LL. B in 1884 and an LL.M in 1885.

His career began at the Treasury Department where he eventually became Secretary-Treasurer. He organized community activities, served as the first president of the Union League of the District of Columbia, published black businesspeople directories, attended the Paris Exposition of 1900, and founded the Correspondence Club, a secret black lobbyist organization. He also found time to tinker in science and engineering.

In 1900, Mr. Hilyer was awarded two patents in water evaporators and accessories for his inventions in air humidification.

“The object of my present invention is to readily supply the heated air of a room with a proper amount of moisture for health and comfort…” – Andrew F. Hilyer, Patent US438159A

Mr. Hilyer’s invention was essentially a water tank and towel that attached to wall registers to moisten the hot, dry air pumping through the heating systems. His invention attached to the front of a wall register (vent) which would blow the warm air through a wet towel, thus, sending evaporated wet, hot air through a room and helped purify the air. The towel acted as a filter which captured and prevented dust/dirt particles from passing through the vent into the home. Mr. Hilyer’s inventions would be cited in numerous modern-day air humidifier inventions, as recent as the 1990s.