Cabin air filters protect those aboard from many biohazards

Aviation International News » September 2003
August 11, 2008, 7:24 AM

As the global marketplace continues to reduce the size of the world, we not only embrace the languages, cuisine and customs of other cultures; we find ourselves in turn embraced by a growing array of deadly airborne pathogens. The most recent was SARS (severe acute respiratory syndrome), which some health officials believe will reappear this winter.

It was determined that the primary cause of SARS was a coronavirus. But before the virus was put in check, 8,437 people worldwide became ill, of whom 813 died. Much blame for the spread of SARS beyond its origins in the People’s Republic of China was attributed to international air travel. Airlines were hit hard as passengers canceled travel plans. Singapore Airlines reported operational losses for the first time in its history, blaming reduced passenger loads. Business aviation travelers also canceled or sharply reduced their travel plans, in particular to SARS-infected areas.

For those in business aviation who are concerned about potential for the spread of such airborne pathogens, at least two companies are now offering what they say is an answer to the threat in the form of simple and effective air-purification systems that can be tailored to fit an existing business jet air-circulation system.

Microgenix introduced its basic unit in early 2000 and the company has rapidly grown from several engineers, including founder and managing director Phillip Hall, in a small south-London office to a staff of 18. And in a search for growth funding, the company has also welcomed a partner. “We realized we were potentially a large company in need of resources,” said Hall, explaining why Microgenix went into a 50/50 venture with Air Filter Technology of New South Wales, Australia. “ATF is totally focused on research and development to meet the growing interest in this air-purification system,” he pointed out.

The Microgenix unit can be as small as a champagne bottle for use in an automobile or tank, or as large as necessary for an airliner or an entire hospital.

The design, which has no moving parts, is deceptively simple. The two-stage process begins with passage of air through a series of three metal filters. Each filter is coated with Biogreen 3000 liquid that dries to create a surface of billions of microscopic spikes. When airborne microorganisms–virus or bacteria– come in contact with the treated filter surfaces, the cell membranes are pierced and they are rendered harmless. The filtered air continues on through a fixed set of impeller blades that create a vortex to increase the “dwell time” for any airborne pathogen in the UV light chamber. This ensures that viruses or bacteria that might have evaded the filters are neutralized by altering their DNA structure.

In early tests by military biological warfare specialists at the Porton Down department of scientific and technology laboratory in the UK, eight billion simulated anthrax spores were put through the purification in one second, with a 100-percent kill rate. The most recent tests at Porton Down earlier this year used simulated tuberculosis and smallpox spores, with a resultant 99.9999-percent kill rate, said Hall.

Existing cabin-air circulation systems use engine bleed air to mix fresh air with up to 50-percent recycled air. That air is passed through HEPA (high-efficiency particulate arresting) filters. When these filters become clogged, their effectiveness can be substantially reduced, requiring replacement as often as three times a year.

Even assuming 24/7 continuous operation, Microgenix suggests replacement of its components–filters and UV bulbs–only once a year, at a total cost of about $300. This can be done at the same time as the recommended annual maintenance check of the system. And Hall added that this maintenance check is primarily to ensure that the monitoring system is working.

Because any bacteria or virus remaining in the filters have been rendered harmless, the used filters do not constitute a biohazard and can be disposed of in any trash receptacle. In fact, they can be washed in a solution provided by Microgenix and reinserted. The entire maintenance and component replacement process is designed to be completed in less than 30 minutes.

Hall said a prototype, weighing about 20 pounds, has already been successfully installed in the existing air-circulation duct system of a business jet as part of the company’s relationship with L-3 Communications of Greenville, Texas.

The company has not yet received an order from the aviation industry, but recently licensed a Canadian company–Microgenix Canada–to build and market the system in Canada. And Hall said talks are in progress with L-3 to oversee certification of the product for the U.S. market. The company, he added, is also searching for a U.S. manufacturer/distributor.

New Filters Product of Space Program

US Global Nanospace of Carson City, Nev., is convinced it has an even better idea, in the form of a new line of virus and pathogen “Nanofilters.”

According to company vice chairman Steven Squires, the Nanofilter is the product of U.S. space program research, with funding from NASA. The core of the technology was initially developed, he said, by Y2 Ultra-Filter for NASA to provide ultra-fine particle matter air filtration. US Global, he added, integrated its own porous Nanofilter “nanofiber” media into the process.

The unit consists of the filter and a metal support structure designed to replace (without modification), an existing aircraft air-purification filter. An electrical current drawing only four watts passes through the metal framework, enhancing the London/Van der Waals particle dispersion properties, including viruses, bacteria, smoke, dust, odorants and other sub-micron-size particulate matter. As the particles move in a churning motion perpendicular to the airflow direction, they are drawn together into larger particles to be filtered.

The final element is the nanofiber covering the filter, “a second science” developed by US Global and able to trap smaller particles without further reducing the airflow pressure. The combination of the Y2 Ultra-Filter technology and nanofiber is “a quantum leap in air filtration,” said Squires.

The Nanofilter is capable of trapping particulates down to the .05-micron level “necessary for effective protection from chemical and biological contaminants,” explained Squires. The SARS virus ranges from .06 microns to .22 microns. He added that tests have proved 99.9999-percent effective down to the .05 micron level.

He also pointed out that in terms of energy conservation, the Nanofilter is expected to provide savings of about 35 percent over the HEPA filters currently in use. For a narrowbody airliner, that would translate to about $96 per flight, and, added Squires, the cost of the Nanofilter will be “competitive with the HEPA filters now in use.” In normal use, US Global expects the filter would have to be replaced with about same frequency as the HEPA filter, based on the number of flights. Initially, the filters must be properly disposed of as biohazard material in keeping with government regulations.

At the same time, US Global is developing an “environmentally friendly” decontaminant that it plans to make available to users. Immersion in the decontaminant would allow the subsequent disposal of the filters as non-biohazard materials.

Squires said US Global is a development company created to provide the filter medium and that the plan is to subcontract the manufacture of the final product.

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