Ever sat on board a commercial aircraft awaiting departure and wonder just what kind of fumes were entering the cabin? Is it just boredom that puts passengers to sleep during longer flights?

People attending the ASHRAE forum on Cabin IAQ were not all on the technical committee, but many had one thing in common: They were concerned about the level of air quality to be found in commercial aircraft cabin areas.

Most of the discussion focused around these areas: jet fumes, biological contaminants, methods currently used to limit exposure to them, and proposed methods to measure cabin air quality.

Within these areas of discussion (but not entered into directly) was this further subdivision: contaminants on the ground and contaminants in the air.

On the ground: jet fumes

Those fumes that passengers smell while the aircraft waits at the gate are a contribution of trimethynol propane phosphate, said a representative from an hvac manufacturer.

While there are no safety limits for exposure to this compound, there is likewise no proof that it’s been found in the cabin.

“We don’t want poison in the cabin,” interjected another attendee. Since there’s a concern and circumstantial evidence that this compound can get into the cabins, “We need to prove that it can’t be produced and moved to the cabin.”

A flight attendant suggested that, in addition to filter maintenance schedules, airlines examine their engine maintenance schedules to make sure that jet fuel fumes are minimized. The attendant suggested that loss of engine fluid (through leaks) could enter cabin air.

There was still more interest in biological contamination from recirculated cabin air in-flight. Thus, the question was raised: “What about colds?”

In the air: biologicals

“We know very much about health issues,” stated an attendee. “Why is no one talking about this?”

Airplane filters have been upgraded, pointed out an attendee from the aircraft community. “For all intents and purposes, they sterilize the air.” He called this “a success story” that has not been told to the public.

Still, an attendee pointed out that public perception is that “Once you get on an airplane, you may as well be kissing everyone else.”

Cases of TB transmission and infection have been reported by the Centers for Disease Control, added another attendee, in which the people who were infected were not sitting close by those passengers who carried the disease. “We must look beyond the filters,” he said.

This brought up the topic of in-flight air contaminant recirculation. Studies need to consider proximity, humidity, and allergens that attach to fabric.

Make no mistake, it’s a very complicated area, and the public is hungry for a standard. The next step is to figure out how to measure cabin IAQ.

One researcher from the manufacturing community pointed out that, according to measured responses and reactions from occupants, used filters in office buildings are more detrimental than new ones, although an old, loaded filter has the seeming capacity to filter out more.

“Can we make people feel better, work better by changing the filter more often? The answer is yes,” both in buildings and, probably, in aircraft.

How to measure so many variables?

One attendee suggested chemical measurement that takes a two-tiered approach:

1. On-board monitoring on every aircraft, 100% of the time; and

2. Periodic monitoring after the measurement of incidence.

The drawback here, however, is that pilots do not have training to carry out this kind of monitoring.

Another commented that chemical concentrations should be measured in order to determine an acceptable concentration (measuring short- and long-term health effects), and examine existing health effect guidelines.

The problem here is that a “maximum” limit will not apply unless there is an immediate health effect. Flight length is a major variable. Therefore, dosage would need to be determined relating to health effect, and adjusted for frequent travelers and/or flight attendants.

“We cannot afford to take the time to advance from chemical to chemical,” said a member of the manufacturing community. “People are impatient for this standard.”

Then there’s the question of air travel and “Sick Building” symptoms. “Are we providing enough fresh air,” asked an attendee. “Does improving airflow reduce symptoms, even though it doesn’t improve perceived air quality?” And what about this proposed minimum 5-cfm outside air ventilation?

There’s a minimum of 15 cfm for indoor environments, pointed out another attendee. “Does that include vehicles? What is the rationale behind 5 cfm?”

One committee member answered that the number came from research from bomb shelters in World War II.

A member of the aircraft community added that the industry is looking at a combination of outside airflow and filtration in order to improve cabin IAQ, comparing air quality and the perception of air quality in flight.

Another attendee asked why measurements are being based on square footage. Researchers need to look at volumes. “We’re not flying auditoriums here,” and the volume of space around occupants is radically different.

Finally, “The dependent variable should not be what you measure,” pointed out an attendee. “It should be how you affect people.”