by Valerie Shore

Commercial airlines need to increase the flow of fresh air to passengers to reduce the risk of disease transmission, says a UVic chemistry professor.

“Over the last 25 years or so there’s been a substantial decrease in the outside air provided in newer aircraft,” says Dr. Martin Hocking, who attracted considerable media attention in early September when he presented a paper on the topic at the Royal Society of Medicine in London.

The paper, “Air Quality of Aircraft Passenger Cabins: Ventilation Trends and Potential,” is based on a literature review, information supplied by airlines, airplane manufacturers and regulatory agencies, and Hocking’s own expertise in ventilation theory and the properties of gases.

“All the evidence suggests that airlines need to reconsider the effect of reduced outside airflow on the comfort and well-being of passengers and cabin crew,” he concludes.

Hocking, an organic chemist with a special interest in environmental chemistry, began studying the quality of airplane air about 10 years ago. A frequent flier, he noticed he would often end up ill at his destination. “It didn’t have to be a long trip. It could happen after a short hop to Edmonton,” he says. Other people told him of similar post-flight maladies.

When Hocking investigated he found that, to cut fuel costs associated with compressing and cooling fresh air, airlines have reduced outside air intake by about one-third over the last three decades. And when smoking was banned during flights about 10 years ago, there was even less incentive for the airlines to provide fresh air.

The airlines now rely more on recirculated air, which is passed through filters to remove particulate matter, including disease organisms. The main problem, says Hocking, is that the filters aren’t changed often enough — usually at one-year to 18-month intervals. “In that length of time, a filter can become a propagating ground for micro-organisms,” he says. By comparison, home heating systems recommend filter changes every month “and they have a far less stringent job to perform than those on aircraft.”

As a result, says Hocking, airline passengers face an increased risk of exposure to viruses such as colds and flu — the most common ailments reported to him by other passengers and flight attendants.
Changing the filters more often would be a good first step, but increasing fresh air flow would be even better, says Hocking. Right now, the average fresh air intake for new aircraft is about 11 cubic feet per minute per passenger, down from 16 on older planes. That means less oxygen and more carbon dioxide in the air, conditions that can lead to fuzzy-headedness, fatigue and even fainting.

In the cockpit it’s a different story. There, the fresh air supply is about 20 to 30 times as much per person as in the passenger cabin. “That’s very reassuring,” says Hocking wryly, “but it tells me that aircraft builders and the airlines know it’s not very good for your alertness to be deprived of fresh air.”

Hocking calculates that it would cost the airlines very little — less than 14 cents per passenger per hour travelled — to restore the fresh air intake to 15 cubic feet per minute per passenger. “If they did that they probably wouldn’t have to recirculate the air, and that has a cost saving because the filters are expensive, and so is the labour to install them.”

But more conclusive research is needed to get the airlines to act, says Hocking. He likens the problem to “sick building” syndrome in the early 1970s when building managers cut back on outside air to save on energy costs. Unaware that the fresh air flow had been dropped to as low as five cubic feet per minute, workers complained of headaches and fatigue. After extensive studies, managers were persuaded to increase the airflow back to 15 to 20 cubic feet per minute. The complaints stopped.

“So do we have to re-invent the wheel with aircraft?” asks Hocking. “It looks like it, yet it seems so evident.”

In the meantime Hocking continues to fly, carefully selecting aircraft that he knows pump in more fresh air. He also travels with a nasal mister filled with distilled water, reasoning that moist nasal membranes are better able to keep out foreign substances. “A number of people I know are doing this now,” he says, “including an ear, nose and throat specialist here in town.”

Copies of Hocking’s paper (in booklet form) are available from the Aviation Health Institute, 17c Between Towns Road, Oxford, 0X4 3LX, England (online at <www.aviation-health.org>).