Two surveys of commercial transportation environments were conducted. In the spring of 1994, environmental conditions on a variety of aircraft over 22 domestic routes were monitored. In 1996, an expanded survey of 27 travel segments was performed on Boeing 777 aircraft, interstate trains, interstate buses, short-distance commuter trains, and subways. A wide variety of environmental measurements were performed including standard Indoor Air Quality (IAQ) parameters of temperature, relative humidity and carbon dioxide (CO₂). Aircraft cabin air pressure was continuously measured. Contaminants including carbon monoxide, particles, and volatile organic compounds (VOC) were monitored or sampled. Surface dust was collected using modified hand vacuums, sifted and the fine particles analyzed for fungi, bacteria, endotoxin and cat and dust mite allergens.

Reasonable correlation between CO₂ levels and passenger loads was observed for travel segments with variable passenger loads, such as trains and subways, which is consistent with fixed volume ventilation. CO₂ levels were stable for the cruise portion of flight segments, but were significantly higher during preflight and post-flight periods, suggesting lower ventilation at times of increased passenger activity.

No significant differences in total fungal concentrations were noted between any transportation modes measured in 1997 or between concentrations in transportation environments and those from living room samples collected during early spring in Boston. Cat allergen was detected in most dust samples with the highest dust mite concentrations recovered from a train. Particle concentrations were highest in subways and generally higher on all ground transportation environments than on aircraft. VOC s associated with mobile sources were higher for ground transportation than for aircraft as were many other VOCs. Exceptions were acetone and ethyl alcohol, which were higher on aircraft.