Research Of Air Purifying Technology Applied In Aircraft Cabins

At a reduced outdoor airflow rate, it should be possible to restore perceived air qualityand alleviate symptoms commonly reported during flight that are related to airpollution by using air purification technology in the air recirculation system, such asphoto-catalytic oxidation and gas-phase absorption.The experiment presented in this report was performed to evaluate the effects of threenew types air purification device at 2.5 L/s/p (5 cfm/person) outside airflow rate.The exposure took place in a ground-level climate chamber whose interior had beenmodified to simulate an aircraft cabin. The cabin consisted of 3 rows of 7 seats.Measurements of environmental parameters, including airflow rate, temperature,relative humidity, CO₂ concentration and a number of volatile organic compoundswere made for each condition tested. By measuring and controlling the physicalparameters, the simulated environment was established. Three different air purifierunits were available for test, two Photo-Catalytic Oxidation units (PCO2 and PCO3)and one gas-phase absorption filter (GPA4). In three conditions, recirculated make-upair was passed through not only a High Efficiency Particulate Air (HEPA) filter butalso one of three air purifier units, while in the reference condition the three unitswere not included in the recirculation system. The subjects for the experimentincluded both male and female, who were evenly distributed in the two age ranges18-30 and 55-70. There were 4 such exposures per experimental condition in abalanced order of presentation of conditions. In each exposure at least 15 and at most21 subjects, on average 17 subjects, were exposed. Thus data from a total of 68subjects, of which 8 were exposed as flight crew, were obtained in each experimentalcondition. Each subject was exposed to the conditions on the same day of the weekand at the same time of day to eliminate variation related to these factors. Theevaluation criteria included subjective assessment of air quality, perception ofenvironmental factors, subjective estimates of SBS symptom intensity and thermalcomfort and noise. Objective medical tests were performed two times daily in order toinvestigate effects on eye, skin and nose function.The objective medical tests showed that nasal peak flow and visual acuity weresignificantly improved by operating GPA4, although the latter only reachedsignificance for the sensitive sub-group. PCO3 had a significant and positive effect onskin dryness. Subjective responses to the cabin environment show that PCO units thatbreakdown VOCs actively and continuously had more positive effects on symptomsthan gas-phase absorption in longer exposures and at higher pollutant levels. TheVOC measurements indicate that intermediate products were generated by theoperation of the PCO units which did not oxidize ethanol completely to CO₂. Thislimits the application of the PCO units examined here in actual flights where cabin airhas a much higher alcohol content than in the simulated aircraft cabin.