In-Flight/Onboard Monitoring: 

ACER’s Component for ASHRAE 

1262, Part 2

Prepared by: 

John D. Spengler, Jose Vallarino, Eileen McNeely, and Hanine Estephan

Harvard School of Public Health

Boston, MA 02215

In cooperation with: 

Ann Louise Sumner

Battelle Memorial Institute

Columbus, Ohio

National Air Transportation Center of Excellence for 

Research in the Intermodal Transport Environment (RITE) 

Airliner Cabin Environmental Research (ACER) Program

April 2012

Final Report

Report No. RITE-ACER-CoE-2012-6
NOTICE

___________

This document is disseminated under the sponsorship

of the U.S. Department of Transportation in the interest

of information exchange. The United States Government

assumes no liability for the contents thereof.

___________

This work was funded by the U.S Federal Aviation Administration

Office of Aerospace Medicine under

Cooperative Agreements 04-C-ACE and 07-C-RITE.

___________

This publication is available in full-text from

the publications Web site of the

National Air Transportation Center of Excellence for

Research in the Intermodal Transport Environment (RITE) at:

www.acer-coe.org
i

Form DOT F 1700.7 (8-72) Reproduction of completed page authorized

1. Report No. 2. Government Accession No. 3. Recipient's Catalog No.

4. Title and Subtitle 5. Report Date

In-Flight/Onboard Monitoring: ACER’s Component for ASHRAE 

1262, Part 2

April 2012

6. Performing Organization Code

7. Author(s) 8. Performing Organization Report No.

John D. Spengler, Jose Vallarino, Eileen McNeely, Hanine Estephan

9. Performing Organization Name and Address 10. Work Unit No. (TRAIS)

Dept of Environmental Health

Harvard School of Public Health

P.O. Box 15677, Landmark 406 West

Boston, MA 02215

11. Contract or Grant No.

07-C-RITE-HU; 04-C-ACE-HU

12. Sponsoring Agency name and Address 13. Type of Report and Period Covered

Office of Aerospace Medicine

Federal Aviation Administration

800 Independence Ave, SW

Washington, DC 20591

Final Report, 2005-2010

14. Sponsoring Agency Code

15. Supplemental Notes

Work was accomplished under Public law 108-76.

16. Abstract

Environmental monitoring was conducted in the passenger cabin of 83 commercial flights (3 additional 

flights as a part of the Onboard Pressure Study). Six aircraft models (2 Airbus and 4 Boeing), flying U.S. 

domestic and international routes, were monitored for environmental conditions and air quality, including 

carbon monoxide, carbon dioxide, particles, ozone, volatile organic compounds (VOCs), semi-VOCs, 

carbonyls, and tricresyl phosphate. Except for low pressure, occasionally high ozone, extremely dry air and 

perhaps slightly higher noise levels, the air quality and environmental conditions in the passenger cabin of 

commercial airplanes are comparable or better than conditions reported for offices, schools and residences, 

with a few exceptions. While most environmental conditions met minimum standards, some exceptions 

were noted, one being the presence of carbonyls (formed in ozone reactions). These and other aldehydes are 

recognized irritants, and together with dry air may contribute to dry eye symptoms and fatigue. 

Concentrations of these ozone-reaction by-products increased with increased ozone levels and with reduced 

ventilation rates. Ventilation rates on high-passenger load flights can be below the required 3.5 

Liters/second/person, as indicated by higher carbon dioxide levels. Some passenger-related VOCs and 

aldehydes were higher for flights with decreased ventilation rates. Cabin pressure was in compliance with 

Federal Aviation Regulations (FARs), with all flights operating below 8,000 feet. Cabin noise levels could 

exceed the NIOSH-recommended level of 85 dB (8-hour time-weighted average) but only for a short period 

of time, but were below the Department of Transportation and OSHA (90 dB) workplace limits.

17. Key Words 18. Distribution Statement

Cabin air quality, ventilation, pressure, temperature, 

ozone, carbon dioxide, VOCs, carbonyls, ultra fine 

particles 

No restrictions

19. Security Classif. (of this report) 20. Security Classif. (of this page) 21. No. of Pages 22. Price

Unclassified Unclassified
ii

ACKNOWLEDGEMENTS

We greatly appreciate the participation of three airline companies and their management, 

flight attendants, and staff that made this assessment of the cabin environment possible—without 

their congenial and professional participation, it would not have been possible to accomplish this 

complex study. We acknowledge the sponsorship of the American Society of Heating,

Refrigerating and Air-Conditioning Engineers and its committee on aircraft ventilation through 

ASHRAE Research Project 1262-RP “Relate Air Quality and Other Factors to Comfort and Health 

Related Symptoms Reported by Passengers and Crew on Commercial Transport Aircraft (Part 2). ACER 

members Sin Ming Loo of Boise State University, Byron Jones of Kansas State University, and Clifford 

Weisel and Charles Weschler of the University of Medicine & Dentistry of New Jersey were particularly 

helpful with instrumentation, research design and analysis support. In addition to Ann Louise Sumner,

assisting the project from Battelle were Jeff Myers, Brad Goodwin, Marcia Nishioka, and Chet Spicer, 

whose efforts were critical to the success of the collaboration. David Space and the Boeing Company 

assisted this study by providing introductions to airlines as well as EMI certification of our instruments.
iii

TABLE OF CONTENTS

INTRODUCTION..........................................................................................................................1

METHODS.....................................................................................................................................1

RESULTS .......................................................................................................................................2

Flight Characteristics ....................................................................................................................2

The Cabin Environment................................................................................................................5

Cabin Pressure.....................................................................................................................5

Ventilation............................................................................................................................6

Ozone .................................................................................................................................11

Temperature.......................................................................................................................14

Relative Humidity...............................................................................................................15

Cabin Noise........................................................................................................................15

Carbon Dioxide and Carbon Monoxide ............................................................................16

Ultrafine Particles .............................................................................................................18

Carbonyls...........................................................................................................................21

Volatile Organic Compounds (VOCs) ...............................................................................23

Tricreysl Phosphate (TCP) ................................................................................................32

Semi-Volatile Organic Compounds (SVOCs)....................................................................32

DISCUSSION...............................................................................................................................35

LIMITATIONS............................................................................................................................44

CONCLUSIONS ..........................................................................................................................44

REFERENCES.............................................................................................................................46

APPENDIX A: Air Sampling Instruments and Analytical Methods

APPENDIX B: Comparisons of Volatile Organic Compounds
1

IN-FLIGHT/ONBOARD MONITORING: ACER’S COMPONENT FOR 

ASHRAE 1261, PART 2

INTRODUCTION

Air quality standards for the aircraft cabin conditions were set decades ago and vary by 

country. In the United States, the airline industry is regulated by the Federal Aviation Agency

(FAA). The FAA has established Federal Aviation Regulations (FARs) to govern the operational 

requirements for commercial aircraft. Currently the FARs address only a few cabin 

environmental parameters that might affect safety aspects of crew performance, and to a lesser 

extent, might protect passengers from adverse health effects and discomfort (pressure, 

ventilation, ozone, carbon dioxide, carbon monoxide). As noted in the 2002 National Research 

Council report (NRC 2002), established FARs may be inadequate to protect the health of some 

members of the flying public. There are design performance standards for environmental control 

systems in aircraft cabins but U.S. airline companies are not required to certify compliance 

through routine direct monitoring or audits. Further, ASHRAE has issued ANSI/ASHRAE 

Standard 161-2007 for air quality within commercial aircraft (ASHRAE 2007). The ASHRAE 

standards include the FAA Federal Aviation Regulations (FARs) (FAA 2011) and also address 

temperature and ventilation in different areas of the aircraft cabin, as well as bleed air 

contaminants. 

This report examines environmental conditions and cabin air contaminants measured on 

83 aircraft, across three different airlines, operating eight airplane models (B737-300, B737-700, 

B737-800, A340, A380, B747, B767 and B777), and compares these conditions and 

contaminants to existing standards as well as other indoor environments. 

METHODS

The cabin air of 83 flights was monitored between February 2008 and August 2010 as a 

component of a FAA/ASHRAE study of onboard environmental conditions and passenger and 

crew responses. These flights were on three different airlines: airline A (20 flights), airline B (39 

flights), and airline C (24 flights). The air contaminants measured included ozone (O3), carbon 

dioxide (CO2), carbon monoxide (CO), ultrafine particles (UFP), particle matter ≤ 2.5 μm 

(PM2.5), volatile and semi-volatile organic compounds (VOCs and SVOCs), aldehydes, and 

tricresyl phosphate (TCP) isomers. Environmental parameters measured included relative 

humidity (RH), cabin pressure (P), temperature (T), and cabin sound levels (dB(A)); operative 

temperature ,which is derived from dry bulb, wet bulb and radiant temperatures, was not 

measured. Monitors were located either in an aisle seat or a middle seat and it was assumed that 

operative temperature equaled the air temperature.

Also collected from the airline during flight was information about flight characteristics, 

including flight duration, flight departure time, aircraft model, flight date and season, aircraft 

capacity and occupancy loads. For flights across the continental U. S., minute-by-minute latitude 

and longitude were obtained from http://flightaware.com/.
2

Exposure assessment was conducted by a project engineer onboard the aircraft. 

Measurements were recorded continuously, at one-minute intervals, from 10,000 feet ascent 

through 10,000 feet descent. In addition, TCP isomers, VOCs, SVOCs, and aldehydes were 

collected via integrated samplers. For each analysis batch, for all analytes except for the VOC 

canisters in airline A, at least five duplicates and five blanks were included to estimate the 

signal-to-noise ratios. Sensors and samplers were situated in the middle of the economy class. 

Instruments with pumps and batteries were positioned under the seat, and VOCs and aldehydes 

samplers were placed at the back of the seat with inlets at seat pocket height of 50 cm. All 

instruments used onboard were electro-magnetic interference (EMI) certified at Boeing (Everett, 

WA). The sensors were also tested for performance under pressure flight conditions at Battelle 

(Columbus, OH). In Appendix A, Table A-1 lists equipment used in this study and Appendix 

Table A-2 lists all the analytes/compounds measured.

The descriptive analysis was performed on the median values of the recorded continuous 

one-minute measurements. Also reported are the overall flight averages and the ranges of these 

median values. VOCs, SVOCs, TCPs and aldehydes were summed separately. A maximum 

hourly value was calculated for ozone for flights with a monitoring duration of 30 minutes or 

more, in order to compare these values with other recently proposed criteria and the hourly FAR 

ozone standard. Running 15-minute averages were calculated for UFPs, reported as particle 

number counts per cubic centimeter for particles ranging in size from 6 nm up to 0.3 μm. 

Latitude categorization was based on the flight path rather than the latitude of the departure and 

arrival cities. Each flight route was classified by the fraction of flight time north of 35°N (or 

south of 35°S). Flights that followed northern routes (higher latitudes) were those that had 

fractions higher than 0.5.

RESULTS

Flight Characteristics

Flight characteristics of the sample set are listed in Table 1. The length of the flights 

varied from 1 hour to more than 16 hours, with 37% of all flights classified as short-haul flights 

(≤ 2 hours). Fifty-eight percent of all flights were at or above 75% load factor (passengers per 

capacity of plane). Of the total flights across all airlines, 20% operated entirely in the southern 

hemisphere, 19% crossed the equator, and 61% operated entirely in the northern hemisphere. 

About 28 flights were routes mostly north of 35°N. Only nine flights (10%) crossed more than 

five time zones. Table 2 lists the summary statistics for the continuous measurements of cabin 

contaminants (O3, CO2, CO and UFPs) and cabin environmental conditions (RH, P, T, and sound 

level).
3

Table 1. Flight characteristics of 83 flights with environmental measurements and surveys collected 

for passengers and crew.

Variables Mean ± SD Range No. (%)

Model of Aircraft 83

 A340 2(2.41)

 A380 5(6.02)

 B737(800;300;700) 41(49.40)

 B747 10(12.05)

 B767 10(12.05)

 B777 15(18.07)

Airlines 83

 airline A 20(24.10)

 airline B 39(46.99)

 airline C 24(28.92)

Duration 83

 Short <3hrs 31 (37.35)

 Medium (3-6hrs) 35(42.17)

 Long(>6hrs) 17(20.48)

Ventilation Rate L/sec/person 5.5 ±1.8 3.0-10.9 83*

 <5 L/sec/person 40(48%)

 >5 L/sec/person 43(52)

Season 83

 Winter 69(83.13)

 Summer 14(16.87)

Latitude 83

 Lower 50(60.24)

 Higher 33(39.76)

Time Zones Crossed 83

 0-1 47(56.63)

 2-5 27(32.53)

 >5 9(10.84)

Occupancy 0.77±0.20 0.23-100 83

 <75% 35(42.17)

 >75% 48 (57.83)

Flights on aircraft fitted with ozone 

converters

83

 Yes 20(24.10)

 No 63(75.90)

*Ventilation was calculated using a G(CO2) value of 18.2 L/hr 
4

Table 2. Summary of continuous measurements of cabin contaminants (ozone, carbon dioxide, 

carbon monoxide and ultrafine particles) and cabin conditions (sound, temperature, relative 

humidity and pressure).

 

*

The WHO Air Quality Guidelines for particulate matter, ozone, nitrogen dioxide and sulfur dioxide (WHO 2006)

state “Ultrafine particles (UF), i.e. particles smaller than 0.1 μm in diameter, have recently attracted significant 

scientific and medical attention. These are usually measured as a number concentration. While there is considerable 

toxicological evidence of potential detrimental effects of UF particles on human health, the existing body of 

epidemiological evidence is insufficient to reach a conclusion on the exposure–response relationship of UF particles. 

Therefore no recommendations can be provided as to guideline concentrations of UF particles at this point in time.” 

Variables Flight

Mean ±SD

Flight

Min-Max

N Standard Limits

Ozone (ppb) 16 ± 18 0-116 81  FAA: 0.25 ppm (250 ppb) anytime 

above 9,800 ft; 0.1 ppm (100 ppb) 

TWA during any 3 h interval

 ASHRAE: 0.05 ppm

 OSHA PEL 0.1ppm

 EPA NAAQS 0.12 ppm (1 h) and 

0.08 ppm (8 hr)

 ACGHIH TWA: 0.05; 0.08; 0.1 ppm 

(heavy, moderate and light work)

 NIOSH: 0.10 ppm

 WHO: 0.06 ppm for 8 h

Ozone 1 h max 27± 32 1.88-210 73  See above listing

Carbon Dioxide (ppm) 1,404 ± 297 863-2,056 83  FAA: 5,000 ppm

 ASHRAE: 700 ppm above ambient 

air

 OSHA PEL: 5,000 ppm

 ACGHIH TWA: 500 ppm; 

30,000 ppm (STEL)

Carbon Monoxide (ppm) ND ND 63  FAA: 50 ppm (sea level equivalent)

 ASHRAE: 9 ppm (8 h); 35 ppm (1 h)

 OSHA PEL: 50 ppm

 EPA NAAQS: 35 ppm (1 h); 

9 ppm (8 h)

 ACGHIH TWA: 25 ppm 

 Fuel fumes should not be present

Ultrafine Particles 

(p/cm3)

616 ± 3,398 0- 24,600 56  No Standard available*

UFP 15 min max (p/cm3) 12,450 ± 43,605 1-312,000 55  No Standard available*

Sound (dB(A)) 74.86±1.91 68.10-76.94 82  OSHA: 90dB (8 h) TWA; PEL (115)

 NIOSH: 85 dB 

 DOT: 90 dB

Relative Humidity (%) 11±5 1.7- 41 83  FAA ventilation design ~18%

Temperature (°C) 24±2.0 19 -31 83  ASHRAE: operative temperature 

(18.3°C to 23.9°C) not to exceed 

 26.7°C

Cabin Pressure (kPa) 80± 2.8 76-88.5 83  FAA: 75 kPa (2,440 m )
5

The Cabin Environment

Cabin Pressure

The FAA Federal Aviation Regulation (FAR) 14CFR25.841 (CFR 2010a) states that the 

minimum cabin pressure under normal operating conditions should not be less than the pressure 

found at an altitude of 8,000 ft (75.3 kPa). The mean cabin pressure across all flights was 79 kPa, 

reaching an average per flight maximum of 88 kPa. None of the 83 flights had pressures below 

75.3 kPa (above 8,000 ft); 68 flights of the 83 had pressures between 82 kPa and 75.3 kPa 

(6,000-8,000 ft); 15 flights had pressures above 82 kPA (below 6,000 ft). Figure 1 shows cabin 

pressure by aircraft models. The B747 cabin pressure was significantly different from all five 

aircraft models with more than five flights. The B747 had an average cabin pressure of 83.9 kPa, 

which was 3.4 kPa higher than the next highest model. The B737-700 had the lowest average 

cabin pressure, 77.8. kPa. The B737-700 cabin pressure was significantly different from other 

aircraft models except the B737-300 (Table 3), with a mean pressure 2.5 kPa above the 75.3 kPa 

standard.

Figure 1. Box plot of cabin pressure (kPa) by aircraft model

75

77

79

81

83

85

87

89

340 380 300 700 800 747 767 777

Aircraft Model

Pressure kPa
6

Table 3. Mean values of cabin pressure (kPa) and t-test P values by aircraft model, for aircraft 

models with at least five flights. Bold denotes a t-test P value of less than 0.05.

Aircraft

B737-

300

B737-

700 A380 B747 B767 B777

mean 78.2 77.8 79.9 83.9 80.5 79.4

B737-

300 0.169 0.434 0.004 0.118 0.268

B737-

700 0.169 0.000 0.000 0.000 0.003

A380 0.434 0.000 0.001 0.051 0.470

B747 0.004 0.000 0.001 0.009 0.023

B767 0.118 0.000 0.051 0.009 0.715

B777 0.268 0.003 0.470 0.023 0.715

Ventilation

FAR 14CFR25.831 (CFR 2010b) states that the ventilation system must provide a 

sufficient amount of uncontaminated air to enable the crew to perform duties without much 

discomfort or fatigue. It specifies that airflow for each occupant must be at least 0.55 pounds of 

fresh air per minute. The FAR related to ventilation has been amended several times since first 

being issued in 1964; the specific ventilation requirements that apply to commercial aircraft are 

dependent upon the date that the manufacturer requests FAA approval and the effective date of 

the amendment. Therefore, aircraft models in operation before issuance of the most recent FAR 

14CFR25.831 may be in compliance even if calculated ventilation rates fall below current 

standards. ANSI/ASHRAE Standard 161-2007 (ASHRAE 2007) describes the ventilation 

requirement as 3.5 Liters/second/person (L/s/p) (7.5 CFM/person) divided by the ventilation 

efficiency, which is assumed to be 1.0 for the interior passenger section, which typically have 

more than six air changes per hour. This ANSI/ASHRAE standard further states that a total air 

supply of 7.1 L/s/p (15 CFM/person) is the minimum, with 9.4 L/s/p (20 CFM/Person) 

recommended. The total air supply can be a mixture of outside air and filtered recirculated air. 

To estimate outside air ventilation rates in the 86 flights (three additional flights from the 

onboard pressure study were added to the 83 onboard flights in this study), we used indoor CO2

using the constant concentration method (ASHRAE 2001) :

Ventilation rate (L/s) = G(CO2) (L/hr) (1)

 (Ci - C0) x 3600 (s/hr)

where:

G(CO2) = resting rate of production of CO2 (L/hr) by an average person; 

Ci = concentration of CO2 measured during flight;

C0 = concentration of CO2 in the outside air.

This method requires the measurements to be collected once the cabin air has equilibrated and 

the cabin CO2 has reached a steady state concentration. CO2 levels were relatively stable in–

flight, suggesting this assumption is valid. The method also requires a value for the CO2
7

generation rate per person. Our review of the literature yielded two slightly different values: 18 

L/hr (ASHRAE 2011) and 13.2 L/hr (Lee and Siconolfi 1994). 

The ASHRAE values for the rate of CO2 generation, G(CO2), were calculated from the 

following equation (Persily1997; ASHRAE 2001; ASHRAE 2011):

G(CO2) = RQ (0.00276ADM)/(0.23RQ+77) (2)

where:

RQ = respiratory quotient: 0.83 for an adult of average size and engaged in sedentary 

activities

AD = DuBois surface area in m2(1.8 m2for an adult of average size)

and AD is calculated as:

AD = 0.203H 0.725 W0.425 (3)

H = height in meters, 

W = weight in kilograms.

 M = Metabolic rate per unit of surface area.

To obtain a G(CO2) value of 18 L/hr, ASHRAE (2001) used a Metabolic rate value (M) of 1.2, 

which corresponds to an adult engaged in light work representing typical office work (The 

ASHRAE Handbook, HVAC applications [2011] uses roughly the same value [0.0105 SCFM = 

17.8 L/hr] in its aircraft calculations).

Lee and Siconolfi (1994) measured G(CO2) on 23 astronauts in a seated position and 

obtained a value of 13.2 L/hr +/- 1.2 L/hr. People in a seated position have an M value of 1 

(Persily 1997). Apart from the difference in M value, the measured G(CO2 ) value (13.2 L/hr) is 

comparable to the ASHRAE G(CO2) assuming 1 M (15 L/hr).

To conduct a sensitivity analysis of the ventilation rate estimates initially calculated using 

point estimate values, we performed a two-part Monte Carlo simulation to obtain a distribution 

of outdoor air flow rate per person for comparison to ANSI/ASHRAE Standard 161-2007 

(ASHRAE 2007). The first part of the Monte Carlo simulation involved determining the 

distribution of the CO2 generation rate per person (G[CO2]) by running simulations of 100-

person flights with a varying mix of travelers. This distribution was then used in the second part 

of the Monte Carlo simulation to estimate a distribution of the ventilation rate (V) for each flight 

in our study. For the first part of the simulation, we ran 10,000 simulations of 100-person flights. 

The model first selected the gender of each occupant (binomial distribution) followed by 

selection of the age of the passenger (discrete distribution). Passenger age was divided into 5 

age groups according to the EPA Exposure Factors Handbook (U.S. EPA 2011a): 20-29 years, 

30-39 years, 40-49 years, 50-59 years, and 60-74 years. After gender and age were selected, the 

height and weight of the passenger were selected by the model based on gender- and age-specific 

distributions of height and weight as reported in the Exposure Factors Handbook (normal 

distribution). 
8

For each passenger, the Dubois surface area (AD) was calculated according to equation 3. 

The AD was then used in equation 2 along with the metabolic rate and respiratory quotient to 

calculate the CO2 generation rate per person (G[CO2]). A constant respiratory quotient of 0.83 

was used. Metabolic rate for each passenger was selected using a uniform distribution derived 

from the metabolic rates presented in Table 4, and based on the 2011 Compendium of Physical 

Activities (Ainsworth et al. 2011).

Table 4. Metabolic rates (METS) by activity type*.

Activity Type Metabolic Rate

Sleeping 0.9 METS

In Bed 0.9-1.37 METS

Sit/Watch TV 1.3 METS

Ride in a bus or train 1.3 METS

*Source: 2011 Compendium of Physical Activities (Ainsworth et al. 2011)

The computational steps from the first part of the simulation are presented in Figure 2. 

Mean G(CO2)for the 10,000 simulations was 18.2 L/hr (standard deviation: 0.3), with a range of 

17 – 19.3 L/hr (Figure 3). 

Figure 2. Steps in first part of the Monte Carlo simulation 

Select Gender 

for 100 People

Select Adult 

Age Group

Select Height 

and Weight

Select 

Metabolic Rate 

(M)

Calculate CO2 generation rate per person (GCO2) for a 100-person flight

GCO2 = RQ(0.00276AdM)/(0.23RQ+77)

Calculate Dubois surface area (AD)

AD = 0.203Height0.725*Weight0.425

Binomial

(50:50)

Discrete

1) 20-29 yrs

2) 30-39 yrs

3) 40-49 yrs

4) 50-59 yrs

5) 60-74 yrs

Normal Dist

EPA Exposure 

Factors 

Handbook 2011

Uniform Dist 

(0.9-1.3)

0.9 Sleeping 

0.9-1.37 Bed

1.3 Sit/Watch TV

1.3 Ride bus/train

Assume 

Respiratory 

Quotient (RQ)

Constant 

(0.83)

(adult of average 

size/sedentary 

activities)

Run 10,000 simulations

Determine Average GCO2 and Standard Deviation

Part I – Determine reliable estimates of CO2 generation rate per person 

(GCO2) using distributions for Height/Weight and MET
9

Figure 3. The mean generation of CO2 for the 10,000 simulations was 18.2 L/hr (standard deviation: 

0.3), with a range of 17 – 19.3 L/hr

The second part of the Monte Carlo simulation used the distribution of CO2 generation 

rates (Figure 4) along with data collected on each of the 86 flights to calculate a distribution of 

potential ventilation rates for each flight (10,000 simulations for each flight). Ventilation rate 

(V) was determined by using equation 1, which included: the measured mean CO2 concentration 

(ppm) on each flight (assuming the average represents steady-state); an assumed outdoor CO2

concentration of 386 ppm, which represents the global monthly outdoor CO2 concentration at 

sea-level as reported by NOAA (Table 5); and the distribution of CO2 generation rates from the 

first part of the simulation. Figure 5 provides an example for six flights showing the central 

estimate of ventilations rate per passenger in liters per second (L/s/p) and the distributions 

derived from the Monte Carlo simulations. Of the 86 flights in our study, six were found to have 

central tendency estimates of ventilation rate below 3.5 L/s/p. In one case, the uncertainty 

around the central estimate had a 95% confident interval that included 3.5 L/s/p. 
10

Figure 4. Computational steps of second phase of the Monte Carlo simulation used to estimate 

ventilation rates

Table 5. Monthly mean global CO2 sea level from NOAA (ppm) for the six months in which 

onboard sampling was performed, ftp://ftp.cmdl.noaa.gov/ccg/co2/trends/co2_mm_gl.txt. The 

uncertainty in the global monthly mean is estimated using a Monte Carlo technique that computes 

100 globally-averaged time series, each time using a slightly different set of measurement records 

from the NOAA ESRL cooperative air sampling network. The reported uncertainty, 0.13 ppm, is 

the mean of the standard deviations for each monthly mean using this technique. (Conway et al 

1994). 

Airline Month Year CO2 ppm

A March 2008 386.0

A July 2008 383.3

B Jan 2009 386.7

B Feb 2009 387.0

C July 2010 388.8

C August 2010 386.0

Flight Indoor CO2

(Ci)

Outdoor CO2

(C0)

G CO2

Calculate Ventilation Rate

Ventilation Rate (L/s/p) = G CO2(L/hr/p) / [ (Ci-C0) x 3600 (s/hr) ]

Flight Number

1

2

3

4

...

86

Measured 

(Mean)

Assumes 

Steady-State 

CO2

Constant

386 ppm

(global monthly 

mean; sea-level; 

NOAA)

Normal Dist.

From Part I 

Monte Carlo 

simulation

Part II – Run simulations for each aircraft with variable GCO2 to determine 

distribution of outdoor air flow rate per person (Vo) in liters per second (L/s)

Run 10,000 simulations for each flight

Determine Distribution of Potential Ventilation Rates
11

Figure 5. Ventilation (Liters/second/person) estimates using Monte Carlo simulation

Ozone

As addressed in FAR 14CFR25.832 (CFR 2010c), cabin ozone levels must not exceed 

0.25 ppm when the aircraft is above 32,000 ft, and a time-weighted average ozone concentration 

should not exceed 0.1 ppm for any 3-hour period when the aircraft is above 27,000 ft. Ozone 

was detected in 73 out of 81 flights with complete records. The average ozone concentration 

across all flights was 15.9 ppb (parts per billion), and the highest average ozone concentration 

within a single flight was 115.6 ppb with minute readings as high as 256 ppb. The maximum 1-

hour ozone value for each flight was calculated from the running hourly (60-min) ozone 

concentrations. Across all flights the mean of the highest hourly value per flight was 27 ppb, 

with the highest 1-hour reaching 210 ppb for a single flight. No flights exceeded the 3-hour 

standard of 0.1 ppm (100 ppb). Figure 6 is the rank ordering of flights by 1-hour ozone levels 

(ppb). It can be seen that aircraft equipped with ozone converters were more likely to be among 

those with lower maximum 1-hour ozone concentrations.

Part II – Run simulations for each aircraft with variable GCO2 to determine 

distribution of outdoor air flow rate per person (Vo) in liters per second (L/s)

Ventilation Estimates using Monte Carlo Simulation

Distribution of 

potential ventilation 

rates based on 

measured CO2

calculated for each 

flight

V11

V50

V53

V 6

V63

V29

0.00

0.04

0.08

0.12

0.16

0.20

0.24

0.28

0.32

0.36

0.40

0.44

Probability

2.4 3.0 3.6 4.2 4.8 5.4 6.0 6.6 7.2 7.8 8.4

Ventilation Rate (L/s/p)

Distribution of Ventilation Rates by Flight

x = 3.5 (0.01%) x = 3.5 (0.01%)
12

Figure 6. Rank ordering of flights by 1-hour ozone levels (ppb). C denotes flights with ozone 

converters.

Only airline A (20 of the total flights) used aircraft fitted with ozone converters. The 

average 1-hour maximum concentration of ozone in aircraft across flights with converters was 

22.3 ppb, while the flights without converters had an average 1-hr maximum ozone of 28.2 (not 

significantly different). The maximum 1-hour ozone concentrations measured per flight was 47 

ppb with converters versus 209 ppb without converters.

Ozone concentrations were significantly higher for flights that followed higher latitude 

routes (>35°N) (average 24 ppb and maximum concentration 115 ppb) versus flights that 

followed lower latitudes (average 10 ppb with a maximum of 39 ppb). Figure 7 displays the 

ozone concentrations by location of the aircraft in flights with a flight path over the U.S. The 

presence of ozone was episodic with the tendency to encounter more ozone at higher latitude 

routes. 

To evaluate the potential for ozone concentrations on flights to exceed the current 

National Ambient Air Quality Standard (NAAQS) and proposed reduction to 60 ppb, we 

calculated ppb-hours for each standard and ppb-hours for each flight (Figure 8). The vast 

majority of flights had ozone exposure concentrations (ppb-hours) that fell well below the 

guidance values. Several flights had ozone exposure concentrations that were approximately half 

of the new proposed standard of 60 ppb (480 ppb-hours). 

0

50

100

150

200

250

CC C C C C C C C C CC C

Flights

Max 1 hour ozone ppb
13

Figure 7. Map of ozone concentrations (ppb) and flight path
14

Figure 8. Total ozone exposure in ppb hours, rank ordered from low to high, for each of the 83 

flights monitored. C indicates the flight aircraft was equipped with an ozone converter.

Temperature

ANSI/ASHRAE standard 161-2007 (ASHRAE 2007) defines the acceptable conditions 

for in-flight temperature, giving the target operative temperature range of 18.3oC to 23.4oC (65oF 

to 75oF), not to exceed 29.4oC (85oF). Temperatures reported in our study reflect seating areas 

away from side walls or galleys. In 72 flights (83% of all flights) the temperature did not exceed

25oC. The average temperature across flights was 24.4°C. Among aircraft (Figure 9), the B737-

700 had the highest average temperature 25oC, with a mean temperature significantly different 

from all aircraft models except the B777 (Table 6). Long and medium duration flights had 

significantly cooler temperatures 23.9oC than flights of short duration 24.8 (P value=0.048). 

Load factor and season were not significantly associated with temperature. Temperature 

fluctuations within flights were associated with the aircraft air warming or cooling after 

departure to a set point or were caused by manual adjustment of the temperature by the flight 

crew. Aside from these temperature changes from one stable set point to another stable set point, 

temperatures in-flight remained stable.

Figure 9. Box plot of temperature (°C) by aircraft model

0.001

0.01

0.1

1

10

100

1000

cc c c c c c c c c c c c cc cc

Ozone ppb hrs

15

20

25

30

35

340 380 300 700 800 747 767 777

Aircraft Model

Temp 

oC
15

Table 6. Mean values of cabin temperature (°C) and t-test P values by aircraft model, for aircraft 

models with at least five flights. Bold denotes a t-test P value of less than 0.05.

Aircraft

B737-

300

B737-

700 A380 B747 B767 B777

Mean 24 25 23 24 24 23

B737-

300 0.032 0.137 0.631 0.212 0.973

B737-

700 0.032 0.023 0.028 0.008 0.418

A380 0.137 0.023 0.224 0.499 0.319

B747 0.631 0.028 0.224 0.451 0.818

B767 0.212 0.008 0.499 0.451 0.542

B777 0.973 0.418 0.319 0.818 0.542

Relative Humidity

FARs and ASHRAE do not provide a standard for humidity in aircraft cabin 

environments because it is recognized that the outside air at flight altitudes is very dry, making a 

humidification requirement impractical. However, ANSI/ASHRAE Standard 161-2007 

(ASHRAE 2007) acknowledges that low humidity can be associated with adverse effects.

The median relative humidity per flight was below 10% for 41 flights and below 18% for 

78 flights, while the average RH across all flights was 11%. Relative humidity was not 

significantly different by aircraft model (Table 7). On mid and long-haul flights, relative 

humidity decreased (13.3% to 9.3%) when compared to short flights (p value =0.007). 

Table 7. Mean values of cabin relative humidity (%) and t-test P values by aircraft model, for 

aircraft models with at least five flights. Bold denotes a t-test P value of less than 0.05.

Aircraft

B737-

300

B737-

700 A380 B747 B767 B777

Mean 9.1 9.7 10.5 8.3 13.7 10.7

B737-

300 0.721 0.469 0.680 0.198 0.219

B737-

700 0.721 0.711 0.388 0.286 0.319

A380 0.469 0.711 0.163 0.350 0.391

B747 0.680 0.388 0.163 0.071 0.074

B767 0.198 0.286 0.350 0.071 0.912

B777 0.219 0.319 0.391 0.074 0.912

Cabin Noise 

Neither FARs 14CFR25 nor ANSI/ASHRAE Standard 161-2007 (ASHRAE 2007) 

address cabin noise. OSHA (29CFR1910.95 [CFR 2010d)]) sets noise limits for the workplace 

as an 8-hour time-weighted average of 90 dB (A) and requires hearing conservation programs be 

available for employees whose time-weighted average exceeds 85 dB (A). The B767 had an 

average sound level of 71.9 dB (A), which was significantly different from all other aircraft 

models except the A380. The A380 had an average sound level of 67.9 dB (A); however with 

the limited number of flights (five) it was not possible to differentiate the A380 from the other 
16

models (Table 8). Sound levels will vary across a cabin, depending on aircraft model, engine, 

thrust mode, and seat location. Our measurements were made at the midpoint of the economy 

section, which varied between aircraft types and carriers. Sound level was not significantly 

different for load factor and flight duration. 

Table 8. Mean values of cabin sound level (dB (A)) and t-test P values by aircraft model, for 

aircraft models with at least five flights. Bold denotes a t-test P value of less than 0.05.

Aircraft

B737-

300

B737-

700 A380 B747 B767 B777

Mean 75.7 75.8 67.9 74.2 71.9 75.5

B737-

300 0.374 0.794 0.485 0.000 0.222

B737-

700 0.374 0.909 0.310 0.004 0.126

A380 0.794 0.909 0.629 0.639 0.564

B747 0.485 0.310 0.629 0.020 0.831

B767 0.000 0.004 0.639 0.020 0.001

B777 0.222 0.126 0.564 0.831 0.001

Carbon Dioxide and Carbon Monoxide (CO2 and CO)

The FARs for ventilation states that the passenger cabin must be free from harmful 

concentrations of gases and vapors (CFR 2101b). It stipulates that CO2 not exceed 5,000 ppm 

and CO not exceed 50 ppm. The average CO2 level during cruise across all flights was 1,404

ppm, with a range of 863 ppm to 2,056 ppm. CO2 was highly correlated with occupancy level 

(Spearman’s r=0.7) and was also associated with relative humidity (Spearman’s r=0.65). CO2 

levels were slightly higher for short-haul flights compared to mid and long-haul flights, but the 

difference was not significant. CO2 levels were not significantly different by aircraft model 

except for the B777. The B777 aircraft had the highest mean CO2 level, 1,499 ppm, which was 

significantly different from all other aircraft models except the B737-300 which had a mean CO2

level of 1,457 ppm (Table 9). These levels are consistent with the ventilation rates previously 

discussed in this report.

Table 9. Mean values of cabin CO2 (ppm) and t-test P values by aircraft model, for aircraft models 

with at least five flights. Bold denotes a t-test P value of less than 0.05.

Aircraft

B737-

300

B737-

700 A380 B747 B767 B777

Mean 1457 1383 1253 1131 1319 1499

B737-

300 0.861 0.563 0.217 0.719 0.115

B737-

700 0.861 0.161 0.067 0.473 0.032

A380 0.563 0.161 0.274 0.846 0.002

B747 0.217 0.067 0.274 0.304 0.003

B767 0.719 0.473 0.846 0.304 0.025

B777 0.115 0.032 0.002 0.003 0.025
17

Figures 10 and 11 show the continuous measurement made during two flights. In the first 

case instruments were operating during the boarding process. Figure 10 shows continuous 

measurements for a B747-400 US continental flight. CO2 levels during boarding reached 1,400 

ppm while averaging about 1,000 ppm during the flight. Figure 11 shows the continuous 

measurements made during a long international flight on a B747. CO2 levels varied by a few 

hundred ppm across the flight, showing a downward trend from mid-flight when many 

passengers were sleeping followed by an increase around and after the time meals were served.

Carbon monoxide was not detected above the instrument’s level of detection of 1 ppm in 

any flight.

Figure 10. Continuous measurements for a B747-400 U.S. continental flight

0

2 0

4 0

6 0

8 0

100

120

11:16 12:28 13:40 14:52 16:04

Time

O3,CO,Temp,RH, Pressure

0

200

400

600

800

1000

1200

1400

1600

CO2

O3ppb

COppm

TempC

%RH

Pressure kpa

CO2ppm

Leave 

Gate 

12:00

Cruise

12:35 Descend 

16:15

10.000 ft 

16:25

747-400

Load Factor 72% 1

1 0

100

1000

10000

100000

11:16 12:28 13:40 14:52 16:04

Time

p/cc
18

Figure 11. Continuous measurements made during a long international flight on a B747

Ultrafine Particles (UFPs)

Ultrafine particles were measured on 55 flights, with a maximum 15-minute 

concentration across flights ranging from 1 p/cc to 312,000 p/cc. UFP levels were quite low for 

most of the flights (< 1,000 p/cm3), and fluctuated with latitude but were not significantly 

correlated with ozone concentrations which did fluctuate with latitude. The mean UFP for flights 

with lower latitude routes was 1,104 p/cc compared to a mean UFP of 55 p/cc for flights with 

higher latitude routes. UFP events were defined as major events having 15-minute averages 

>10,000 p/cc, and minor events having 15-minute averages between 500 and 10,000 p/cc. For 

flights which had no food preparation onboard (an activity expected to raise UFP), both minor 

and major UFP events were associated with elevated ozone (Table 10). Out of 39 flights with no 

food preparation on board only two had both major and minor UFP events, and four flights had 

only minor UFP events. 

For flights with meal service, the association between UFP and ozone was not as 

evident, probably because meal preparation aboard these flights confounded any chance of 

observing a relationship. Eight of 22 flights had major and minor UFP events, one flight had 

only major UFP events, and four flights had only minor UFP events. All events were associated 

with meal preparation and were of moderate or long duration. Figure 11, which shows a long 

international flight with meal service, demonstrates periodic short duration spikes in UFP during 

typical meal times. Episodic variation in UFP might be associated with switchover in bleed air 

from pressure in the Environmental Control System or variations in engine power. However, it 

was not possible to discern these events during the course of air monitoring in the cabin.

0

5

10

15

20

25

30

11:00 13:24 15:48 18:12 20:36 23:00

T, RH, CO

0

500

1000

1500

2000

2500

CO2, O3, BP UFP

T C

%RH

CO ppm

CO2ppm

BP Hpa

O3 ppb

UFP p/cc

Meal service 12:00

Meal service 21:20

Announced change in cruise altitude at 

20:22 from 35,000 to 38,000

747

Load Factor 66%
19

Table 10. Major and minor UFP (p/cc) events and ozone concentration (ppb) 

P/cc 

Event Type

N (minutes) Mean ozone 

(ppb)

Median 

ozone( ppb)

Maximum 

ozone (ppb)

5

th Percentile 

ozone (ppb)

No Food 

preparation

Major 

>10,000 p/cc

130 74 63.7 126.7 30.3

Minor

<10,000 p/cc

>500 p/cc

97 45.4 35.0 118.2 20.6

>500 p/cc 3982 16.9 9.8 152 3.6

Meal Service

Major 

>10,000 p/cc

194 4.4 47 16.6 1.0

Minor

<10,000 p/cc

>500 p/cc

609 10.9 5.5 92.3 2.1

>500 p/cc 6979 15.9 7.5 131.1 1.4

The relationship between particle generation in the presence of ozone is illustrated for a 

flight that originated in Colorado and flew through an upper level trough, descending from 

Canada over the upper mid-west on its way to the mid-west. Figure 12 shows the synoptic 

weather features (12a), the flight path (12b), the maximum and minimum temperatures for the 

day (12c), the 500 mb heights (12d), and the precipitation for 7:00 a.m. on the flight date (12e). 

Figure 13 plots ozone ppb and UFP p/cc at flight altitude in this cabin. Ozone starts off low with 

no detectable UFPs, and about 30 minutes into the flight ozone begins to rise, exceeding 60 ppb 

for 45 minutes, before decreasing on descent. The UFP levels increased sharply after ozone 

levels increased, reaching UFP of 25,000 p/cc through the remaining cruise time, then UFPs also 

decrease as ozone sharply decreases upon descent.
20

Figure 12. The association of particle generation with ozone is illustrated for a flight that originated 

in Colorado and flew through an upper level trough (descending from Canada over the upper midwest) on its way to the mid west. This figure shows the synoptic weather features (12a), the flight 

path (12b), the max and min temperatures for the day (12c), and the 500 mb heights (12d) and 

precipitation for 7:00 a.m. on the flight date (12e).

Figure 13. Ozone, ultrafine particle and altitude data for the flight between Colorado and the mid 

west in which ozone-initiated particle formation was observed 

a b

c d e

0

10

20

30

40

50

60

70

80

90

100

Time

8:338:408:478:549:019:089:159:229:299:369:439:50

Time MST

Ozone PPB

0

5000

10000

15000

20000

25000

30000

35000

40000

45000

Atitutude (ft) Ultrafine (p/cc)

Ozone ppb

Altitude (ft)

Ultrafine p/cc
21

Carbonyls 

A total of five carbonyls (acetaldehyde, acetone, acrolein, formaldehyde, 

propionaldehyde) were monitored but not all of them in each flight. Table 11 presents a summary 

for just three carbonyls (acetaldehyde, formaldehyde, propionaldehyde) which were sampled 

using the same method on airlines B and C. Acetaldehyde was detected in 81% of the samples 

(airlines B and C only); acetone was detected in 79% of the samples (all airlines); acrolein was 

detected in 71% of the samples (airlines A and C only); formaldehyde was detected in 49% of 

the samples (airlines B and C only); and propionaldehyde was detected in 17% of the samples. 

See Appendix B, Table B-1, for a summary of the percent of detection for all the carbonyls (as 

well as volatile organic compounds) sampled across all three airlines.

Table 11. Descriptive statistics of carbonyls sampled in airlines B and C only; all other carbonyls 

are presented in Appendix B, Table B-1.

N Percent

detected

Q25 Minimum Median Maximum Q75

Formaldehyde 70 35 1.90 0.00 2.71 11.72 4.18

Acetaldehyde 70 57 4.46 0.86 7.40 75.79 17.08

Propionaldehyde 70 29 1.25 0.00 2.18 8.87 3.34

There were no significant differences between aircraft models for acrolein, acetone and 

formaldehyde. Figure 14 shows plots of the carbonyl samples by aircraft model. Table 12 

presents the results of statistical analysis of differences for acetyaldehyde among aircraft models. 

In the B737-700, the mean concentration of acetalaldehyde was 20.3 μg/m3, which was 

significantly different from the mean concentrations in the A380 (8.0 μg/m3), B747 (8.3 μg/m3) 

and B767 (5.5 μg/m3). The A380 aircraft cabin also had a significantly different mean 

acetaldehyde concentration from the B767. Similarly, Table 13 shows the differences between 

aircraft models for propionaldehyde. The B737-300 aircraft mean propionaldehyde 

concentration was 3.4 mg/m3. This was significantly different from the mean concentrations for 

A380 (1.3 μg/m3), the B747 (1.7 μg/m3), and the B767 (1.9 μg/m3) aircraft. The A380 mean 

propionaldehyde concentration (1.3 μg/m3) was also significantly different from the B737-700 

mean concentration (2.7 μg/m3). 
22

Figure14. Plots of carbonyl concentrations (μg/m3) by aircraft

Table 12. Mean acetaldehyde concentration (μg/m3) and t-test P values by aircraft model, for 

aircraft models with at least five flights. Bold denotes a t-test P value of less than 0.05 

Aircraft B737-300 B737-700 A380 B747 B767

Mean 13.2 20.3 8.0 8.3 5.5

B737-300 0.222 0.273 0.342 0.121

B737-700 0.222 0.002 0.007 0.000

A380 0.273 0.002 0.886 0.017

B747 0.342 0.007 0.886 0.266

B767 0.121 0.000 0.017 0.266

0

10

20

30

40

50

60

70

80

90

B737-

300

B737-

700

B737-

800

A340 A380 B747 B767 B777

Aircraft

Acetone mg/m

3

0

10

20

30

40

50

60

70

80

B737-

300

B737-

700

B737-

800

A380 B747 B767

Aircraft

Acetaldehyde mg/m

3

0

2

4

6

8

10

B737-

300

B737-

700

B737-

800

A380 B747 B767 B777

Aircraft

Propionaldehyde mg/m

3

0

2

4

6

8

10

12

14

B737-

300

B737-

700

B737-

800

A380 B747 B767

Aircraft

Formaldehyde mg/m

3

0

10

20

30

40

50

60

B737-

800

A340 A380 B747 B767 B777

Aircraft

Acrolein mg/m

3
23

Table 13. Mean values of cabin propionaldehyde concentration (μg/m3) and t-test P values by 

aircraft model, for aircraft models with at least five flights. Bold denotes a t-test P value of less 

than 0.05.

Aircraft B737-300 B737-700 A380 B747 B767 B777

Mean 3.4 2.7 1.3 1.7 1.9 2.1

B737-

300 0.368 0.019 0.035 0.048 0.212

B737-

700 0.368 0.042 0.098 0.135 0.527

A380 0.019 0.042 0.571 0.321 0.377

B747 0.035 0.098 0.571 0.662 0.584

B767 0.048 0.135 0.321 0.662 0.746

B777 0.212 0.527 0.377 0.584 0.746

Flight characteristics affected some of the concentrations. Some compound 

concentrations varied by flight duration and ventilation but not by seasonality. Short flights were 

significantly different for propionaldehyde (p=0.002) only, with an average of 3.6 μg/m3for 

short flights and 1.7 μg/m3for long flights. Acetone levels were significantly different (p=0.025) 

for flights with greater than 90% occupancy (30.4 μg/m3) compared to flights with less than 90% 

occupancy (23.3 μg/m3). Formaldehyde and acetone levels were significantly different for 

flights with ventilation rates less than 6.0 L/s/p compared to flights with ventilation rates greater 

than 6.0 L/s/p: 3.7 μg/m3compared to 2.4 μg/m3for formaldehyde (p value = 0.042); and 27.8 

μg/m3compared to 20.2 μg/m3for acetone (p value = 0.026). 

Volatile Organic Compounds (VOCs)

VOCs were sampled using evacuated canisters for airline A and thermal desorption tubes 

for airlines B and C. The target analytes and the number and percent of samples above the 

detection limit for each airline can be found in Appendix B, Table B-1. Overall for compounds 

measured on all three airlines, toluene was detected in 91% of the samples, followed by carbon 

tetrachloride and tetrachloroethene in 90% of the samples. M&p-xylene was detected in 75% of 

the samples. Benzene, ethylbenzene, o-xylene, methylene chloride, hexane, and styrene were 

detected in 50% to 75% of the samples. Table 14 lists the descriptive statistics of VOCs sampled 

on all three airlines. Table 15 lists the mean values of VOCs measured on all three airlines and 

the t-test p-values from comparisons among airlines. 
24

Table 14. Descriptive statistics of volatile organic compounds by airline (ng/m3).

airline airline airline

A B C

25th Min Median Max 75th 25th Min Median Max 75th 25th Min Median Max 75th 

Non-chlorinated

1,3-butadiene 0 0 0 44 0 126 0 618 212715 6173 8 0 534 50408 1760

methyl tert-butyl ether 0 0 0 86 6 14 0 35 16163 196 0 0 19 3662 493

benzene 537 0 876 3286 1176 259 0 548 20073 1471 0 0 116 62341 3012

toluene 1886 1007 2783 30028 4388 1926 463 2846 115378 6426 6077 119 10105 132926 15745

ethylbenzene 123 0 187 575 277 134 60 230 13452 501 272 0 418 3855 652

m&p-xylene 224 152 333 715 519 487 206 956 28674 1896 762 0 1120 9387 2381

o-xylene 103 73 163 419 236 129 0 291 14174 484 273 0 409 3441 758

Chlorinated

methylene chloride 168 0 45641 661819 196325 761 19 2842 46533 5925

chloroform 0 0 35 535 95 80 21 138 2089 275 0 0 95 1955 458

1,1,1-trichloroethane 0 0 10 26 15 53 0 63 1852 119 0 0 31 560 111

carbon tetrachloride 23 0 28 38 31 561 0 649 1704 877 430 0 639 2796 855

trichloroethene 14 0 21 653 31 68 0 324 29448 1399 0 0 132 41286 2329

cis-1,3-dichloropropene 0 0 0 0 0 0 0 0 2104 0 0 0 0 527 0

trans-1,3-dichloropropene 0 0 0 0 0

tetrachloroethene 274 54 619 1928 915 810 68 1166 10007 2600 3443 1177 10670 123025 13318

1,4-dichlorobenzene 122 42 187 701 283 170 51 322 2420 593 44 0 307 12738 769

Other

acrolein 1978 0 2976 5969 4086 1681 0 3207 52773 8775

acetone 19643 13702 23563 53157 29667

2-butanone 1888 1273 2154 4051 2588 823 0 1356 11500 2421

ethanol 807338 221100 1433770 4916004 2213250

ethyl acetate 1026 360 1751 7140 2567 5131 0 16132 29969

hexane 198 0 262 700 444 2962 38 68360 1123078 153401 0 0 0 1517

Isoprene 1818 1056 2225 5637 3337 8500 705 14316 49932 18574

isopropyl alcohol 2147 0 3095 32021 4495 2896 0 6312 84029 23898

styrene 83 40 161 503 228 275 112 369 3391 620 149 0 416 12083 900

airlines B and C only

2-Methylpentane 409 9 2042 392507 3800 0 0 76 49673 2074
25

airline airline airline

A B C

25th Min Median Max 75th 25th Min Median Max 75th 25th Min Median Max 75th 

2-Methylhexane 107 8 174 16467 395 47 0 128 1304 691

2,3-Dimethylpentane 31 10 73 9544 184 48 0 101 1179 271

3-Methylhexane 53 0 118 19670 325 67 0 175 62330 634

2,2,4-Trimethylpentane 375 121 979 29019 1514 376 0 867 69137 1506

Methylcyclohexane 58 24 114 5211 280 104 0 274 5223 537

airline A only

propylene 898 0 1148 71959 1382

methyl bromide 0 0 0 3241 37

Methyl methacrylate 0 0 0 1999 0

1,2,4-trimethylbenzene 157 55 208 1397 298

dichlorodifluoromethane 267 247 282 1018 295

tetrahydrofuran 0 0 0 1484 93

cyclohexane 93 0 110 939 202

methyl chloride 567 0 629 757 694

vinyl acetate 188 0 290 759 425

carbon disulfide 425 0 571 800 672

Heptanes 40 0 61 577 98

trichlorofluoromethane 117 114 124 400 138

1,3,5-trimethylbenzene 36 19 56 303 75

2-hexanone 0 0 81 347 188

trans-1,2-dichloroethene 0 0 0 360 80

1,3-dichlorobenzene 0 0 0 224 11

methyl isobutyl ketone 0 0 169 619 320

4-ethyl toluene 34 15 51 229 70

chlorobenzene 0 0 0 217 20

ethyl chloride 0 0 0 250 0

1,2,4-trichlorobenzene 0 0 16 69 30

1,1,2-trichlorethane 0 0 0 76 0

1,2-dichlorobenzene 0 0 0 72 12

1,1,2,2-tetrachloroethane 0 0 0 59 0

1,1,2-trichloro-1,2,2-

trifluoroethane 26 24 31 46 33

bromoform 0 0 0 34 0
26

airline airline airline

A B C

25th Min Median Max 75th 25th Min Median Max 75th 25th Min Median Max 75th 

benzyl chloride 0 0 0 69 0

hexachlorobutadiene 0 0 0 21 2

1,2-dichloroethane 0 0 0 50 0

1,2-dichlorotetrafluoroethane 0 0 4 22 7

dibromochloromethane 0 0 0 18 0

1,2-dibromoethane 0 0 0 20 0

bromodichloromethane 0 0 0 11 0

vinyl chloride 0 0 0 0 0

1,1-dichloroethene 0 0 0 0 0

1,1-dichloroethane 0 0 0 0 0

cis-1,2-dichloroethene 0 0 0 0 0

1,2-dichloropropane 0 0 0 0 0

1,4-dioxane 0 0 0 0 0
27

Table 15. Mean values (μg/m3) and t-test P values for VOC comparisons between airlines (for 

VOCs measured in all three airlines). P values in bold are less than 0.05.

Mean A Mean B Mean C Airlines

A-B

Airlines

A-C

Airlines

B-C

Mean Concentrations

(μm/m3)

P-Values

VOCp (MTBE, benzene, 

toluene, ethylebenzene, 

m/p xylene, and o-xylene)

10.16 5.07 6.75 0.05 0.12 0.25

chlorinated compounds 3.01 1.17 3.45 0.00 0.32 0.01

MTBE 0.02 0.24 0.12 0.07 0.02 0.23

Benzene 1.03 0.72 0.90 0.15 0.42 0.40

Toluene 7.65 3.01 4.95 0.04 0.16 0.13

ethylbenzene 0.40 0.23 0.14 0.08 0.00 0.20

m/p xylene 0.71 0.62 0.49 0.36 0.05 0.29

chloroform 0.20 0.06 0.07 0.03 0.03 0.42

trichloroethene 0.12 0.46 0.66 0.05 0.06 0.31

1,4-dichlorobenzene 0.54 0.11 0.17 0.00 0.00 0.28

Hexane 0.49 50.00 1.02 0.00 0.30 0.00

A variable representing the sum of hydrocarbons that may originate from petroleum 

combustion was created. There were no significant differences among the sum of the petroleum 

hydrocarbons, summarized as “VOCp” (MTBE, benzene, ethylbenzene, toluene, m&p-xylene, 

and o-xylene). Hexane was not included in this sum since the values for hexane were much 

greater than the values of the other compounds. Airline B had a significantly higher mean 

hexane value than airlines A and C. For the sum of the chlorinated compounds (chloroform, 

carbon tetrachloride, trichloroethene and 1,4-dichlorobenzene), airline B had a significantly 

lower mean concentration than both airlines A and C. For toluene, airline A was significantly 

higher than airline B. For ethyl benzene, airline A was significantly higher than airline C. 

Dichlorobenzene and chloroform were significantly higher in airline A than in airline B and C. 

Airline C had a significantly higher mean MTBE concentration than airline A. The mean MTBE 

concentration of airline B was higher than Airline C, but because of the higher variance in the 

MTBE values in airline B, the p-value comparing airline A to C was 0.07. As would be 

expected, flights with ventilation rates lower than 6.0 L/s/p had a mean VOCp of 8.0 μg/m3

which was significantly different (p-value = 0.004) to flights with ventilation rates higher than 

6.0 L/s/p with a mean VOCp concentration of 3.3 μg/m3. 

Three large surveys of VOCs collected in other indoor settings were used to compare the 

VOCs measured in the cabin air. In the Building Assessment Survey Evaluation (BASE) study, 

the EPA conducted a large exposure and health survey of 100 U.S. office buildings. In the 

Toxic Exposure Assessment Columbia-Harvard (TEACH) study, researchers measured VOCs in 

residences in New York City and Los Angeles; the Los Angeles data was readily available for 
28

comparison to the cabin air data. In the Boston Exposure Assessment in Microenvironments 

(BEAM) study, researchers investigated VOC levels in homes and other indoor environments in 

the Boston area. Specific comparisons are graphically displayed in this report while summary 

tables are available in Appendix B. Table B-2 (Appendix B) compares the median values in the 

EPA BASE Large Building Study (Brightman et al. 2008) to the median values measured in each 

airline. The BASE building values were higher for most compounds except for methylene 

chloride in airline A, hexane in airline B and ethyl acetate, toluene and tetrachloroethene in

airline C. Table B-3 (Appendix B) compares cabin VOC measurements to outdoor data 

collected and analyzed with similar methods in the TEACH Los Angeles Study (Sax et al. 2004), 

as well as the BEAM study conducted in the greater Boston metropolitan area (Dodson et al. 

2007). Median values and 75 percentile values were generally either comparable or lower in the 

cabin air than in the two sets of outdoor data, while the cabin air maximum values were generally 

higher than the outdoor maximum values. VOC concentrations by aircraft type were compared 

to the median and 95th percentile values from TEACH and BASE data. The comparisons for 

select VOCs are presented in Figure 15 through 17 (Note: boxplots depict the median, 25th/75th

percentiles, 5th/95th percentiles, and outliers). 
29

Figure 15. Box-plot distributions of VOC concentrations by aircraft type in comparison to the 

Building Assessment Survey and Evaluation (BASE) and the Toxic Exposure Assessment:

Columbia-Harvard (TEACH) normative data for homes/offices. The BASE and TEACH bar 

represents the median BASE/TEACH value. VOCs shown did not exceed the BASE and TEACH 

95th percentile values (not included in the figure). 

1,4-Dichlorobenzene

340380737747767777 BASE Median TEACH Median

Concentration (μg/m

3

)

0

2

4

6

8

10

12

14

1,1,1-Trichlorethane

340380737747767777 BASE Median TEACH Median

Concentration (μg/m

3

)

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

-m & -p Xylene

340380737747767777 BASE Median TEACH Median

Concentration (μg/m

3

)

0

2

4

6

8

10

o-Xylene

340380737747767777 BASE Median TEACH Median

Concentration (μg/m

3

)

0

1

2

3

4

5

Formaldehyde

380737747767 BASE Median TEACH Median

Concentration (mg/m

3

)

0

2

4

6

8

10

12

14

16

18
30

Figure 16. Box-plot distributions of VOC concentrations by aircraft type in comparison to the 

BASE and the TEACH normative data for homes/offices. The BASE and TEACH bar represents 

the median BASE/TEACH value. VOCs shown did not exceed the BASE and TEACH 95th

percentile values (not included in the figure). 

Acetone

340380737747767777BASE TEACH

Concentration (μg/m

3

)

0

20

40

60

80

100

120

Toluene

340380737747767777BASE TEACH

Concentration (μg/m

3

)

0

20

40

60

80

100

120

140

Chloroform

340380737747767777BASE TEACH

Concentration (μg/m

3

)

0

1

2

3

4

5

6

Styrene

340380737747767777BASE TEACH

Concentration (μg/m

3

)

0

2

4

6

8

10

12

14
31

Figure 17. Box-plot distributions of VOC concentrations by aircraft type in comparison to the 

BASE and TEACH normative data for homes/offices. The BASE and TEACH bar represents the 

median BASE/TEACH value. VOCs shown did not exceed the BASE and TEACH 95th percentile 

values (not included in the figure).

Benzene

340380737747767777BASE TEACH

Concentration (μg/m

3

)

0

10

20

30

40

50

60

70

Tetrachloroethene

340380737747767777BASE TEACH

Concentration (μg/m

3

)

0

20

40

60

80

100

120

140

Trichloroethene

340380737747767777BASE TEACH

Concentration (μg/m

3

)

0

10

20

30

40

50

Carbon Tetrachloride

340380737747767777BASE TEACH

Concentration (μg/m

3

)

0.0

0.5

1.0

1.5

2.0

2.5

3.0
32

Tricresyl Phosphate (TCP) 

TCP samples were collected only for airlines B and C, and TCP was detected in only one 

airline B sample, 0.1 ppt (T[m]CP). Detection limits were calculated as the higher value of 

either three times the standard deviation of the field blanks or the method detection limit for each 

target compound. A summary of the results is shown in Table 16. For airline C TCP analysis, 

two additional isomers identified by De Nola et al. (2008) as constituents of jet engine oil were 

added to the target analyte list.

Table 16. Limits of detection and percentage of samples above the LOD for TCP analysis (total 

N=71 samples). 

Batch 1 Batch 2

% Samples

Target Compound LOD (ng) LOD (ng) N > LOD > LOD

airline B N=16 N=19

T(o)CP 0.9 0.4 0 0

T(m)CP 0.64 0.4 1* 2.8

T(p)CP 0.74 0.4 0 0

airline C N=19 N=17

T(o)CP 0.4 0.4 0 0

T(m)CP 0.4 0.4 0 0

T(p)CP 0.4 0.4 0 0

T(m,m,p)CP 0.4 0.4 0 0

T(m,p,p)CP 0.4 0.4 0 0

* The one sample detected of T(m)CP in airline B was at 0.1 ppt.

Semi-Volatile Organic Compounds (SVOCs)

SVOCs were sampled on 63 flights of airlines B and C, but final results are available for 

only 21 flights of airline B, as of this report date. The remaining SVOCs samples from airline B 

were analyzed only for flame retardants under a separate project. Over-recovery of analytes 

from matrix spike QA samples from airline C are still under investigation. Table 17 lists the 

target analytes and the number of samples above the limit of detection (LOD), and Figure 18 

presents box plots of the SVOC samples. Fragrance-related SVOC (SVOCf) detected in the 

flight samples were: hexyl cinnemal, AHTN, HHCB and benzyl acetate. The concentrations of 

these four SVOCf’s exhibited an inverse relationship with ventilation (Figure 18), but due to the 

limited number of samples and detection limits no significant association can be inferred. 
33

Table 17. Number and percentage of samples above the LOD for SVOCs measured in 21 flights in 

airline B. SVOCf are underlined.

N > LOD % >LOD N > LOD % >LOD

Diethyl Phthalate 19 86 AHTN 17 77

Dibutyl Phthalate 5 23 PCB 52 7 32

Butyl Benzyl Phthalate 5 23 Fluoranthene 4 18

Di-2-Ethyl Hexyl 

Phthalate

5 23 Pyrene 5 23

Limonene 19 86 Tris(dichloro)phosphate 4 18

Phenethyl Alcohol 0 0 Benzo(a)anthracene 6 27

Benzyl Acetate 16 73 Chrysene 3 14

Naphthalene 15 68 4,4'methylene bis(ochloroaniline)0 0

Biphenyl 16 73 Sumithrin 1 5

Acenaphthene 14 64 cis-Permethrin 3 14

Fluorene 17 77 trans-Permethrin 3 14

Hexyl cinnemal 17 77 Benzo(b)fluoranthene 3 14

Tris(2-

chloroethyl)phosphate

6 27 Benzo(k)fluoranthene 2 9

PCB 11 3 14 Benzo(e)pyrene 1 5

Phenanthrene 17 77 Benzo(a)pyrene 5 23

Anthracene 7 32 Dibenzo (a,h)anthracene 2 9

HHCB 17 77 Indeno(1,2,3-cd)pyrene 2 9

Benzo(ghi)perylene 3 14
34

Figure 18. Box plots of SVOCs (ng/m3) measured on 21 flights on airline B

1

10

100

1000

10000

100000

1000000

Diethyl PhthalateLimoneneDibutyl PhthalateButyl Benzyl PhthalateDi-2-Ethyl Hexyl

Phthalate

Benzyl AcetateNaphthaleneHexyl cinnemalHHCBAHTN

Tris(2-

chloroethyl)phosphate

Compound

ng/m

3

0

5

10

15

20

25

30

35

40

45

50

Phenethyl AlcoholBiphenylAcenaphthyleneAcenaphtheneFluorenePCB 11PhenanthreneAnthracenePCB 52FluoranthenePyreneTris(dichloro)phosphBenzo(a)anthraceneChrysene4,4'methylene bis(oSumithrincis-Permethrintrans-PermethrinBenzo(b)fluorantheneBenzo(k)fluorantheneBenzo(e)pyreneBenzo(a)pyreneDibenzoIndeno(1,2,3-Benzo(ghi)perylene

Compound

ng/m

3
35

DISCUSSION

Cabin environmental conditions were monitored on 83 commercial flights which varied 

by aircraft model, passenger load factor and several other flight-specific characteristics. Except 

for low pressure, and occasionally high ozone, extremely dry air and perhaps slightly higher 

noise levels, the air quality and environmental conditions in the passenger cabin of commercial 

airplanes are comparable or better than conditions reported for offices, schools and residences, 

with a few exceptions. While most environmental conditions met minimum standards, some 

exceptions were noted. Further, reported for the first time are carbonyls formed in ozone 

reactions. These and other aldehydes are recognized irritants, and together with dry air may 

contribute to dry eye symptoms and fatigue.

Pressure levels did not exceed the lowest limit of 75.3 kpa (cabin equivalent altitude of 

8,000 ft) required by the FAR 14 CFR 25.841 (CFR 2010a), and overall were similar to cabin 

pressures reported previously, ranging between 72 kpa and 100 kpa (Spengler et al. 1997;

Cottrell et al.1995). Cabin pressure did vary among the different aircraft models. Even though 

cabin pressures complied with FAA FAR regulation, more recent evidence on healthy subjects 

associated prolonged durations at reduced pressure (even below the threshold of 8,000 feet 

equivalent, i.e. 7,000 feet altitude) with moderate oxygen desaturation. Muhm et al. (2007) 

reported a decrease of approximately 4.3% between 7,000 and 8,000 feet that contributed to 

increased discomfort in unacclimated participants after 3 to 9 hours. 

The aging population of air travelers underscores the importance of understanding the 

effects of mild hypoxia in older healthy and health-compromised passengers. Related ACER 

research studied the blood oxygen saturation response of such individuals during a 5-hour 

simulated flight in a hypobaric chamber with pressurization equivalent to a commercial flight at 

7,000 feet altitude (McNeely et al. 2011). These typical cabin pressures resulted in moderate 

desaturation in vulnerable seniors. Importantly, current medical guidelines for determining 

passenger fitness to fly and the need for in-flight supplemental oxygen underestimated the 

prevalence of desaturation during flight found in this study. While current medical guidelines 

consider baseline health conditions, health status (i.e., healthy senior or cardiac patient) did not 

predict the degree of desaturation during flight. However, health status was associated with the 

level of compensatory response and significantly different compensatory responses were seen in 

cardiac patients, suggestive of greater physiological loads. Furthermore, passengers with cardiac 

disease experienced greater frequency of arrhythmias at cabin altitudes. These results suggest 

that longer flight durations (i.e., greater than the 5-hour duration evaluated in these studies) may 

be even more stressful for healthy and unhealthy seniors, especially when flying to high altitude 

destinations. In all, the pressure studies have identified the potential need for added protections 

for senior flyers either in terms of revised rule-making for cabin altitudes, recommended 

guidelines for use of supplemental in-flight oxygen, or accepted use of personal monitors that 

measure oxygen saturation in order to prevent moderate hypoxia in vulnerable passengers.

The Aerospace Medical Association, Aviation Safety Committee released a position 

paper recommending further research about the effects of mild hypoxia for passengers and for 

these worker groups in particular (Aerospace Medical Association 2008). A number of research 

studies have shown performance decrements between 5,000 and 10,000 feet, notably at altitudes 
36

below the current requirement for supplemental oxygen. In addition, the aging workforce of crew 

and pilots may be vulnerable because of the reduced oxygen capacity related to aging and 

because of the increased metabolic demands for oxygen in crew as they push utility carts down 

the aisles of jumbo planes at 34,000 feet.

In sum, the current FAA regulations for limiting cabin pressures to 8,000 feet equivalent 

altitudes allow for mildly hypoxic conditions. These environments are expected to have little 

effect on healthy passengers, pilots or crew, however, older individuals and persons with 

compromised cardiopulmonary status may be at risk. More than thirty years has passed since the 

thresholds for pressure were set. In the meantime, new composite materials in the fuselage that 

withstand greater pressure differential between the cabin and outside air provide a potential for 

reducing the maximum cabin altitude to less than 8,000 feet. Newer aircraft are able to fly higher 

and for longer periods, extending the exposure to hypoxia. The need for closing these gaps in 

information has never been more important given the rise in older and health compromised 

passengers. 

The ventilation system must be designed to provide each occupant with an airflow 

containing at least 0.55 pounds of fresh air per minute according to the FAR14 CFR 25.831

(CFR 2010b) and 3.5 L/s/p according to ANSI/ASHRAE 161-2007. Using measured CO2 to 

calculate ventilation rates, the majority of the flights were in compliance with the 3.5 L/s/p 

standard set by ASHRAE (2007). In six cases the central estimate for ventilation rates were

below 3.5 L/s/p. However, CO2 is not a perfect proxy for ventilation since it is contingent upon 

the occupancy density, assumed exhaled CO2 rate, and mixing efficiency. Measurements were 

made in the mid-section of economy class seating and for these calculations of ventilation rates 

the air mixing effectiveness within the cabin was assumed to be unity. While the turnover rate of 

cabin air is quite high (every 6 to 12 minutes) mixing of the air within the cabin may not be 

uniform, resulting in a mixing efficiency less that one. To the extent that internal mixing 

efficiencies are not equal to 1.0 the ventilation calculated here may be 

underestimated/overestimated. 

Estimated ventilation rates presented here did not account for the presence of young 

children with lower CO2 generation rates. We do not have information about the age and gender 

composition of the monitored flights. However, including children in these estimates would bias 

ventilation rate estimates downward in proportion to age adjusted CO2 generation rates. 

CO2 generation rates are known to be a function of metabolic oxygen demand. If a significant 

number of passengers slept during flight, then the CO2 generation rates would be lower than 

those used in this report and the estimated ventilation rates would need to be adjusted downward. 

The FAR requirements set a design criterion for the ECS based on 0.55 lbs of air per minute per 

passenger at full load. While some flights had estimated ventilation rates below the equivalent 

3.5 L/s/p, it does not imply that the FAR was being violated for those flights since the FAR that 

applies to a specific aircraft depends on which FAR amendment was in effect when that model 

was in design. Also, the presence of CO2 in the cabin from dry ice, if not accounted for, would 

result in a downward bias in estimates of ventilation rates.

Flights with higher passenger load factors had higher CO2 levels and hence lower 

ventilation rates. Across the aircraft models in this study, estimated ventilation rates varied from 
37

about 3 L/s/p to > 10 L/s/p. The study did not include commuter fleets or some models reputed 

to have lower ventilation rates (i.e., B757), so generalizing to the current fleet of commercial 

aircraft is limited. Additional factors that influence internal mixing within the cabin are CO2

generation rates for different metabolic activities for a more age and gender diverse passenger 

composition; accounting for these factors will further refine estimates of ventilation rates.

Even with these limitations, the concentrations of several contaminants appeared to be 

inversely proportional to estimated ventilation rates. These include the sum of a subset of 

SVOCs identified as related to fragrances, carbonyls produced by ozone reactions, as well as 

some VOCs. The first interpretation that has merit is that these compounds have sources related 

to humans since they also demonstrate proportionality to passenger load factor. Ventilation rates 

were not associated with ozone and ultrafine particle concentrations, which were more episodic 

and independent of passenger loads.

While recognizing the limitations of this particular study it is important to consider the 

role of ventilation and transmission of infectious agents. Recently, an expert panel convened by 

ASHRAE critically reviewed the literature and concluded that there were associations between 

low ventilation rates and an increased risk of allergies, sick building syndrome (SBS) symptoms 

and respiratory infections (Sundell et al. 2011). It is not clear at this time whether the cabin 

environment’s high air exchange rates and HEPA filtration mitigates against airborne disease 

transmission. 

While ambient atmospheric levels of ozone at cruising altitudes of commercial aircraft 

can exceed 0.5 ppm at times these high levels are not seen in the passenger cabin (Spengler et al. 

2004). Ozone is unstable and is removed in the bleed air system and by deposition to surfaces 

(ASHRAE 2007; Coleman et al. 2008). However, removal rates may not always be sufficient to 

remove all ozone so elevated ozone in cabin air can occur. Ozone levels are sufficient to react 

with unsaturated hydrocarbons that may also be present in the cabin air (Weschler et al. 2007). 

 The majority of the time ozone levels were in accordance with FAR, 14CFR25.832

(CFR 2010c): only one flight approached the maximum ozone instantaneous FAR ozone level of 

0.25 ppm (250 ppb); and three flights exceeded the maximum allowable 1-hour level (100 ppb). 

The ozone-related FARs were established in 1980. Since then there have been substantial 

advancements in the scientific evidence on the health effects of ozone (U.S. EPA 2011b).

 EPA’s Clean Air Scientific Advisory Committee (CASAC) recommended that the 

NAAQS for ozone be set within a range of 60 to 70 ppb over 8 hours. In a March 30, 2011 letter 

to EPA Administrator, Lisa Jackson, CASAC Chair Jonathan Samet asserted that their review of 

the ozone health literature shows “no threshold” or level below which there is no risk of 

decrement in lung function (Samet 2011). CASAC points out that even in healthy individuals 

clinically relevant responses have been shown at 60 ppb exposure. Large segments of the 

population include asthmatics, children, and elderly individuals with chronic lung and heart 

disease who are more vulnerable to increased exposure. None of these conditions would exclude 

individuals from flying, thus it is reasonable to begin a review the now three-decade old ozone 

FAR.
38

The World Health Organization for European States issues ambient air quality guidelines 

(WHO 2010). Table 18 summarizes their more serious findings on ozone exposure (note that 100 

μg/m3is equivalent to 50 ppb ozone concentration). The WHO findings on adverse effects for 

exacerbation of symptoms for asthmatics and increased hospital admissions for respiratory 

conditions occur at concentrations reported for that aircraft cabin environment.

Table 18. Health outcomes associated with changes in ozone concentrations in epidemiological 

studies.

Health Outcome Change in O3 concentration μg/m3

1-hour averaging 

time

8-hour averaging 

time

Increase in symptom exacerbation 

among adults or asthmatics (normal 

activity)

25% 200 100

50% 400 200

100% 800 300

Increase in hospital admissions for 

respiratory conditionsa

5% 30 25

10% 60 50

20% 120 100

a

Given the high degree of correlation between the 1-hour and 8-hour ozone concentrations in the field 

studies, the reduction in health risk associated with decreasing 1-hour and 8-hour ozone levels should be 

identical (WHO 2010).

Since commercial aircraft fly at altitudes where ozone concentrations might be greater 

than those typically found at ground level, some planes are equipped with ozone (catalyst) 

converters. A new converter dissociates approximately 95% of the ozone in the bleed air and has 

a useful life of 12,000 flight hours (ASHRAE 2007). In this study, one airline equipped its 

aircraft with ozone converters and these passenger cabins had a mean maximum 1-hour ozone 

value of 16.9 ppb compared to 26.5 ppb for flights without converters. While ozone was higher 

in flights without converters, most flights remained in compliance with FAR14CFR25.832 (CFR 

2010c). Aircraft encounters with high ambient ozone air masses are episodic so cabin ozone 

levels exceeding WHO-recommended values may occur. This study, while confirming 

observations on cabin ozone reported elsewhere, cannot be used to infer the frequency at which 

elevated ozone occurs in commercial flights. 

The passenger cabin air temperature average for all flights (24.6oC) was higher than the 

passenger cabin temperature (22oC) reported in previous studies (Lee et al. 1999; Lindgren and 

Norback 2002). Cabin temperatures are typically higher than the temperature set points for 

offices to compensate for the lower relative humidity.

The relative humidity average for all flights (11%) was lower than values listed in the 

literature, which range from 15% to 19% (NRC 2002; Lee et al. 1999; Lindgren and Norback 

2002; Boschi and Haghighat 2005; Lee et al. 1999). Nordstrom et al. (1994) found that in 
39

hospital settings increases in relative humidities from ranges of 25% to 35% to 40% to 45% 

significantly reduced airway symptoms. In a double-blind study, Lindgren, Norbäck and 

Wieslander (2007) increased the relative humidity in a B767 by 10% in the forward part of an 

airplane, and by 3% in the aft section and cockpit. Seventy-one crew members participated in a 

randomized trial of outbound and returning international flights. When the humidification 

device was operating, the cabin was perceived as being less dry (P=0.008), and fresher 

(P=0.002). The authors comment that their findings were consistent with workplace studies 

where a modest 10% increase in relative humidity (to 30-40%) in the winter decreased the 

sensation of dryness. 

Fang and co-workers (1998) demonstrated that subjects had a more favourable perception 

of air with lower enthalpy (cooler and drier) than air that was warmer with more moisture. 

While the range of temperatures tested in their experiments were typical of those experienced on 

an airplane, the lowest humidity levels were only 30%. By extrapolation passengers would 

experience cabin air with lower enthalpy than Fang and co-investigators created in their test. 

Fang et al. (1998) started with “clean air” in the absence of typical indoor sources that emit 

chemical compounds/odors. They found that in the presence of these indoor sources study 

participants could readily detect the presence of irritating odors when the air was cooler and 

drier. Furthermore, sources acted additively, degrading the perception more in air with lower 

enthalpy. Perception of cabin air quality should be quite favorable for “clear air” conditions. 

The introduction of sources such as body metabolites, “dirty” seats and carpets, personal care 

products, cleaning compounds, jet exhaust, and bleed air contaminates would be more readily 

recognized and considered objectionable when present in the conditioned air of the cabin 

environment.

Importantly, some viruses have been shown to thrive in low humidity environments at 

similar levels to the mean levels found in this study. Past research on the influenza virus has 

focused on airborne viruses and generally suggests that survival and/or transmission is facilitated 

by low relative humidity (Weber and Stilianakis, 2008). The influenza virus has been found to 

persist in the environment for hours to days, allowing for secondary transmission of influenza via 

inanimate objects known as fomites. How long viruses survive on fomites is important to 

transmission potential when an uninfected person contacts that surface. The survival of viruses 

on surfaces is influenced by temperature and humidity. In a recent publication, Shaman and 

Kohn (2009) concluded that absolute humidity is the controlling factor in both the inactivation of 

influenza virus and the transmission of influenza. Further study about virus transmission in the 

cabin environment is warranted. 

The sound level measured inside the aircraft was within the recommended level of 85dB 

(A), however this threshold considers 8-hour exposures only and offers little guidance for 

extended flights. A few studies have investigated sound levels inside the aircraft cabin. Spengler 

et al. (1997) found that sound levels ranged between 80 and 85dB. Küpper et al. (2010) reported 

that noise levels were below 85 dB(A) inside an ambulance version of a Learjet 35A while the 

levels of the noise produced by the engines outside the cabin were significantly above 85 dB(A). 

Sound levels in the B767 were lower than sound levels measured in other aircraft models, both 

wide and narrow body aircraft, with the exception of the A380. Too few A380 flights were 

monitored to draw statistical inference but sound measurements in the economy section appeared 
40

to be systematically lower than similarly recorded measurements in other aircraft models. 

Aircraft noise is becoming a well-recognized issue and more modern aircraft have been 

redesigned to dampen noise levels by 4 dB (Holzman 1997). Considering the technological 

advances that now permit ultra-long flights, such as 22 hours, the attention to noise exposures is 

increasingly important, especially when considering concomitant exposure to turbulence and 

vibration. These exposures excite the central nervous system and have been shown to increase 

blood pressure, heart rate, and cause sleep disturbances, with effects that last after the exposure 

(Babisch 2006). Notably, noise regulations are generally set to address problems with hearing 

loss only.

Carbon dioxide levels were above the recommended levels set by ASHRAE (2007) but

below the 5,000 ppm limit mandated by the CO2 FAR, 14CFR 25.831 (CFR 2010b). However, 

the maximum values were slightly higher than values reported in the literature, which were 1,100 

ppm - 1,700 ppm (NRC 2002; Lee et al. 1999; Lindgren and Norback 2002). Carbon dioxide 

levels in excess of 1,000 ppm, once thought benign, have recently been investigated (Satish et al.

2011). Twenty-two subjects were exposed in a double-blind chamber study to three levels of 

carbon dioxide: ambient room conditions with 600 ppm CO2; 1,000 ppm ultrapure CO2; and 

2,500 ppm ultrapure CO2. After a period of acclimatization, subjects took the Measurement of 

Decision Making Performance: Strategic Management Simulation (SMS) to evaluate executive 

decision making. This computer simulation has various possible scenarios with tasks that are 

potentially complex and volatile, have ambiguity, and have delayed feedback. The SMS has 

been used widely in professional settings, including health care, as it provides results on 

parameters for “decision making” (e.g., responsiveness, initiative, emergency responses, 

planning, strategy, etc.). The Satish et al. (2011) study is the first to examine the effects of 

moderate levels of CO2 on executive decision making as measured by SMS. Figure 19 shows 

the overall performance across several functional groups of human decision making. The 

findings, if substantiated, have particular relevance to the airplane environment where CO2 levels 

are typically between 1,000 ppm and 1,500 ppm (or higher) for extended periods. Satish and 

collaborators (2011) found statistically significant decrements in decision making performance at 

1,000 ppm CO2 that were of a magnitude to be important at the societal level. Larger decrements 

in decision making performance were observed at 2,500 ppm CO2. These results are broadly 

consistent with the prior findings of Kajtar et al. (2006).
41

Figure 19. Results of decreased performance with exposure to CO2 (after Satish et al. 2011)

Recent evidence has shown that ozone might react with unsaturated hydrogen 

compounds, such as those compounds found in furniture cleaning products, to form ultrafine 

particles, aldehydes and other compounds (Weschler et al. 2007; Wisthaler et al. 2005). In our 

study, ultrafine particles showed a positive trend with ozone, and in the absence of meal 

preparation, ozone was strongly associated with UFPs. Meal preparation has been noted by the 

flight scientists as a source of UFP generation, and Lindgren et al. (2007) noticed a regular but 

moderate increase in UFP counts (100 to 200 p/cm3) when flights attendants heated bread and 

foods in the microwaves. These researchers also found that the concentration of UFPs varied 

within and across flights, reaching up to 300,000 particles/cm3.

†

Evidence that ozone reactions 

are occurring is seen in the samples for ozone by-products: 6-methyl-5-heptene-2-one, octonal, 

nonanal and decanal, as measured on airline B. Figure 20 plots the concentration of 6-methyl-5-

heptene-2-one versus ventilation for flights with total ozone exposures less than 35 ppb-hrs and 

flights greater than 35 ppb-hrs. Figure 21 plots the concentration of 6-methyl-5-heptene-2-one, 

octanal, nonanal, and decanal against ventilation for flights with total ozone exposures less than 

 

†

The WHO Air Quality Guidelines for particulate matter, ozone, nitrogen dioxide and sulfur dioxide (WHO 2006)

state “Ultrafine particles (UF), i.e. particles smaller than 0.1 μm in diameter, have recently attracted significant 

scientific and medical attention. These are usually measured as a number concentration. While there is considerable 

toxicological evidence of potential detrimental effects of UF particles on human health, the existing body of 

epidemiological evidence is insufficient to reach a conclusion on the exposure–response relationship of UF particles. 

Therefore no recommendations can be provided as to guideline concentrations of UF particles at this point in time.” 
42

35 ppb-hrs and flights greater than 35 ppb-hrs. Thirty-five ppb-hrs is the median ozone total 

exposure over all 32 flights with ozone byproduct samples. Both plots show the concentrations 

of these compounds are affected by the presence of ozone as well as the ventilation. The flights 

with more than 35 ppb-hrs ozone have 6-methyl-5-heptene-2-one have on average concentrations 

four times higher than those with less than 35 ppb ozone. The three other ozone by-products 

measured: octanal, nonanal and decanal show similar relationships though not as strong (Figure 

22). The eye and airway irritation of these reactive species need to be evaluated in the context 

of co-occurring ozone and these compounds. 

Figure 20. Cabin ventilation (Liters/second/person) plotted against cabin concentration 6-methyl-5-

heptene-2-one (6-MHO), in ppb, for flights with a total ozone exposure less than 35 ppb hrs and 

flights with a total ozone exposure greater than 35 ppb hrs for 26 of the 32 airline B flights with

detectable levels of 6-MHO. 35 ppb hrs was the median total ozone exposure for the 32 flights. 

Ventilation was of calculated using a G(CO2) value of 18.2 L/hr.

Figure 21. Cabin ventilation (L/s/p) plotted against the sum of the cabin concentrations of 6-

methyl-5-heptene-2-one, octanal, nonanal and decanal (in ppb) for flights with a total ozone 

exposure less than 35 ppb hrs and flights with a total ozone exposure greater than 35 ppb hrs for 26 

of 32 airline B flights with detectable levels of the sum of the four compounds. 35 ppb hrs was the 

median total ozone exposure for the 32 flights. Ventilation was calculated using a G(CO2) value of 

18.2 L/hr.

0

2

4

6

8

10

12

0 5 10 15

Ventilation (l/s/person)

6methyl5heptene2one (ppb)

<35 ppb hrs O3

>35 ppb hrs O3
43

Figure 22. Box plot of ozone by-product concentrations with flights less than (n=16) and greater 

(n=16) than 35 ppb hr ozone exposure

Many of the VOC compounds concentrations were lower in the passenger cabin than 

what is typically reported of offices and residences (Brightman et al. 2008). The maximum 

levels of formaldehyde, m&p-xylene and o-xylene and acetone, averaged across flights, were

higher than values previously reported inside aircraft cabins (Nagda and Rector 2003). Acetone 

and formaldehyde levels were correlated with ozone concentrations, suggesting that VOCs may 

undergo a chemical reaction in the presence of ozone. Elevated ethanol concentrations were 

consistent with previous studies that have attributed these levels to a large number of people 

inside a smaller cabin space and the service of alcoholic beverages during flight (Nagda and 

Rector 2003). The maximum range of acetaldehyde reported in the literature was between 

26.4 μg/m3and 30.7 μg/m3in bleed air, and between 20.8 μg/m3and 70.2 μg/m3in the cabin air 

(NRC 2002). Acetone, tetrahydrofuran and isopropyl alcohol levels were lower than previously 

reported by Spengler et al. (1997).

There were some unexpected findings where the concentrations of several chlorinated 

compounds were higher for some models then found in indoor air. For example carbon 

tetrachloride and tetrachloroethene were elevated in the A380, B747 and B767 samples 

compared to the BASE (Brightman et al. 2008) and TEACH studies (Sax et al. 2004). 

Trichoroethene appeared higher in the A380 and B767 samples. The presence of chlorinated 

VOCs in the cabin environment needs to be explored further. It is unclear whether these 

compounds are associated with aircraft materials, cleaning practices (routine or during C-Check), 

or personal care products and clothing brought on board by passengers. Benzene was higher for 

the A380 in comparison to concentrations reported for offices and homes. There were a few 

0

5

10

15

20

25

octanal O3<35ppbhroctanal O3>35ppbhr

nonanal O3<35ppbhrnonanal O3>35ppbhr

decanal O3<35ppbhrdecanal O3>35ppbhr

6-MHO O3<35ppbhr6-MHO O3>35ppbhr

ppb
44

higher benzene concentrations found in the B767 samples as well. Toluene, another aromatic 

hydrocarbon, also showed higher levels in the A380, B747 and B767 samples. On occasion 

measurements taken on B737s showed elevated of aromatic compounds including 1,3-butadiene 

and MTBE. The reason for these aberrantly high values is unknown.

The 2004 Institute of Medicine report stated that there was insufficient data to establish 

the relationship between exposures to VOCs and the development of exacerbation of asthma 

(IOM 2004). Papers published after the IOM (2004) report was published offer some evidence 

linking VOCs to asthma and allergenic disease. A study of Australian children by Rumchev and 

co-workers (2004) linked an increase in VOC exposures to asthma symptoms. Dales and 

Raizenne (2004) in a literature review reported consistent findings of a relationship between 

VOCs and indicators for asthma. Additionally, Hulin and colleagues (2010) suggested that 

VOCs indoors are associated with increased asthma risk. Formaldehyde exposure has been 

associated with acute effects on eyes, nose and throat irritation. Vulnerable populations to 

formaldehyde exposures include children with allergic conditions (Hagerhed-Engman et al. 2006; 

Kulle 1993). Other links with VOC’s and asthma have been reported by Dodson et al. (2012), 

Choi et al. (2010), and Bornehag et al. (2004). 

LIMITATIONS

While continuous measurements were conducted for all the environmental conditions and 

most of the air contaminants, measurements on aldehydes and VOCs were performed only once, 

using integrated samplers. Notably, the sensors and samplers were positioned only in one 

location inside the cabin. Ventilation rates were estimated based on 100% ventilation efficiency 

rate and assumed that occupants are the only source for CO2 inside the cabin. Also, we assumed 

that cabin air temperature was to equal to the operative temperature, in order to be able to 

compare it to the ASHRAE operative temperature standard.

Spatial variations in environmental conditions within the cabin could not be assessed in 

this study. If there were uneven distribution of sources, this might be an issue limiting 

generalization of our results. While some sources, like those associated with galleys, might lead 

to concentration differences in various sections of the cabin, the high overall air exchange rates 

of aircraft through a mechanical distribution system designed to supply air throughout the cabin 

certainly promotes a well-mixed environment. Thus, sampling location in the middle of 

economy class was not a limitation for the U.S. domestic flights.

CONCLUSIONS

 Despite the challenging task of recruiting airlines to participate in the FAA/ASHRAE 

onboard study of cabin environments, three forward-looking carriers did permit assessments of 

cabin environmental conditions and passenger/crew perceptions during regularly scheduled 

commercial flights. Environmental monitoring was conducted on 83 flights and 4,306 passenger 

surveys. All flights maintained cabin altitudes below 8,000 feet.

 
45

 Carbon dioxide values ranged from 863 to 2,056 ppm during cruise and were highly 

correlated (r2=0.7) with load factors. While still very much below the 5,000 ppm limit set by 

FARs (FAA 2011), recent studies show impaired cognitive function at CO2 exposures in the 

range of 1,000 ppm to 2,500 ppm, raising concerns about possible diminutions of flight crew 

performance that needs further evaluation. 

Ventilation rates were calculated from the mean CO2 levels measured during cruise. 

Estimating ventilation rates in this way has some inherent uncertainties, as has been discussed in 

this report. Nevertheless, calculations suggest that 7% of the flights monitored had estimated 

ventilation rates lower than ASHRAE 161-2007 recommended levels. Compliance with FAR 

14CFR25.831 (CFR 2010b) could not be determined. The relationship among airplane 

ventilation rates, air pollutant concentrations, passenger perceptions of cabin air quality and 

airborne disease transmission need further study.

This study offers further evidence that cabin ozone levels can exceed the FARs and that 

ozone converters will substantially reduce the chance for high excursions. For the first time, 

direct evidence of ozone chemical reactions forming irritating carbonyls and ultrafine particles in 

aircraft cabins is presented. The role that these compounds and ultrafine particles play in 

passengers’ perception of air quality or contribute to irritation related symptoms remain to be 

investigated. 

Organophosphates, in the form of tricrysel phosphate (TCP) isomers, in cabin air were

assessed in this study. No flight in this study experienced an incident of smoke or fumes in the 

cabin. Thus, the TCP samples taken on 63 flights, with analytical methods able to detect the o-, 

m- and p-TCP isomers at sub ppb levels, are only able to document background levels on 

commercial flights. Only one sample had a detectable level (0.1 ppt [parts per trillion]) of one of 

three isomers. For this single case T(m)CP was detected at sub ppb concentration. No 

conclusions can be made about the magnitude or frequency of exposures to TCP isomers that 

might occur as a consequence of a smoke-in-cabin incident. Background levels of three TCP 

isomers in cabin air of commercial flights, based on this study, are in the subparts per billion 

concentration range.

This onboard study of environmental conditions in the passenger cabin of commercial 

flights, along with evidence on health, irritation and discomfort of exposures to some of the 

environmental conditions that have emerged since many of the FARs related to cabin air quality 

were established, suggests that FAA ought to rigorously review the adequacy of current FARs. 

In fact, the first recommendation in the National Research Council (2002) report The Airliner 

Cabin Environment and the Health of Passengers and Crew called upon the FAA to provide 

“quantitative evidence and rationales to support sections of the FARs that establish air-qualityrelated design and operational standards for aircraft (standards for CO, CO2, O3, ventilation, and 

cabin pressure)”. Results presented in this study may be interpreted as showing that for these 

selected set of flights there was general compliance with the FARs. However, the understanding 

of health effects and irritation has progressed substantially since most of the current FARs were

established. The change in crew and passenger demographics over the years, reflecting the aging 

of U.S. populations, has implications for vulnerability to cabin conditions. Contaminants not 
46

previously recognized or measured in the cabin environment have now been documented and 

will need to be considered in a review of some FARs.

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APPENDIX A

In-Flight/Onboard Monitoring: ACER’s Component for 

ASHRAE 1262, Part 2

Air Sampling Instruments and Analytical Methods
Appendix A Page 1

Table A-1 List of Equipment

Instrument

Variable Measurement Mode Manufacturer

Model 

Number

Operating 

Range Precision Accuracy

1 Ozone Continuous 2B Technologies 205 1.5 ppb -100 ppm ± 1. ppb ± 1. ppb

2 Relative 

humidity/Temp

Continuous TSI 7565 Qtrak 0–95%

32 140 Fo

± 3%

1 Fo

± 3%

1 Fo

2 Carbon 

monoxide

Continuous TSI 7565 Qtrak 0 - 500 ppm ± 3 ppm ± 3%

2 Carbon dioxide Continuous TSI 7565 Qtrak 0 5,000 ppm ± 500 ppm at 

low end of scale

± 3%

2 Pressure Continuous TSI 7565 Qtrak 688-1238 mb 2% of reading 2% of 

reading

3 Pressure Continuous Setra 278-500 500 – 1500 mb ± 0.04mbar ± 0.6mbar

4

(

Noise Continuous Quest 1100 30-140 dB 1 dB ± 0.5 dB

5 Motion Continuous Crossbow 

Technology

CXTLA02 ± 20° 0.03° ± 5%

(est)

6 Respirable 

particles

Continuous TSI SidePak 

AM510

1 mg/m3– 20 

mg/m3

± 1 mg/m3

7 Volatile 

organic 

compounds 

(VOCs)

Integrated samples BGI Omni pump Omni cc/min orifice

(20 min 

sampling)

± 5% ± 5%

7 Semi-volatile 

organic 

compounds 

(SVOCs)

Integrated samples BGI Omni pump Omni 8 L/min ± 5% ± 5%

8 and 9 Data 

Acquisition

Continuous Onset HOBO 

U12-006

4 channels 0-2.5 

Volts

2 mv or 2 % of 

reading

2 mv or 2 

% of 

reading
Appendix A Page 2

Table A-2 List of target analytes

1,1,1-trichloroethane benzo(k)fluoranthene limonene

1,1,2,2-tetrachloroethane benzyl acetate m&p-xylene

1,1,2-trichloro-1,2,2-trifluoroethane (Freon-113) benzyl chloride methyl bromide (bromomethane)

1,1,2-trichloroethane biphenyl methyl chloride (chloromethane)

1,1-dichloroethane bromodichloromethane methyl isobutyl ketone (4-methyl-2-pentanone)

1,1-dichloroethene bromoform (tribromomethane) methyl methacrylate

1,2,4-trichlorobenzene butyl benzyl phthalate methyl tert-butyl ether

1,2,4-trimethylbenzene carbon disulfide methylcyclohexane

1,2-dibromoethane carbon tetrachloride (tetrachloromethane) methylene chloride (dichloromethane)

1,2-dichlorobenzene chlorobenzene naphthalene

1,2-dichloroethane chloroform (trichloromethane) nonanal

1,2-dichloropropane chrysene octanal

1,2-dichlorotetrafluoroethane (Freon-114) cis-1,2-dichloroethene o-xylene

1,3,5-trimethylbenzene cis-1,3-dichloropropene PCB 11

1,3-butadiene cis-permethrin PCB 52

1,3-dichlorobenzene cyclohexane phenanthrene

1,4-dichlorobenzene decanal phenethyl alcohol

1,4-dioxane di-2-ethyl hexyl phthalate propene

2,2,4-trimethylpentane dibenzo (a,h)anthracene propionaldehyde

2,3-dimethylpentane dibromochloromethane Pyrene

2-butanone (methyl ethyl ketone) dibutyl phthalate styrene

2-hexanone (methyl butyl ketone) dichlorodifluoromethane (Freon-12) Sumithrin

3-Methylhexane diethyl phthalate tetrachloroethene

4,4'methylene bis(o-chloroaniline) ethanol tetrahydrofuran

4-ethyl toluene ethyl acetate toluene

6methyl5heptene2one ethyl chloride (chloroethane) trans-1,2-dichloroethene

acenaphthene ethylbenzene trans-1,3-dichloropropene

acetaldehyde fluoranthene trans-Permethrin

acetone fluorene trichloroethene

acrolein formaldehyde trichlorofluoromethane (Freon 11)

AHTN heptane tri-m,m,p-cresyl phosphate

anthracene hexachloro-1,3-butadiene tri-m,p,p-cresyl phosphate

benzene hexane tri-m-cresyl phosphate

benzo(a)anthracene hexyl cinnemal tri-o-cresyl phosphate

benzo(a)pyrene HHCB tri-p-cresyl phosphate

benzo(b)fluoranthene Indeno(1,2,3-cd)pyrene tris(2-chloroethyl)phosphate

benzo(e)pyrene isoprene (2-methyl-1,3-butadiene) tris(dichloro)phosphate

benzo(ghi)perylene isopropyl alcohol vinyl acetate

vinyl chloride (chloroethene)
Appendix A Page 3

Continuous Instruments

Ozone

The Model 205 Ozone Monitor (2B Technologies, Boulder Colorado) was used to 

measure ozone. It is measures ozone ranging from low ppb (precision of ~1 ppb) up to 

250,000 ppb (0-250 ppm) based on the technique of absorption of UV light at 254 nm. It 

uses two detection cells to improve precision, baseline stability and response time. UV 

light intensity measurements Io (ozone-scrubbed air) and I (unscrubbed air) are made 

simultaneously, which makes it possible to reduce the time between ozone measurements 

to 2 seconds. Fast measurements are especially desirable for aircraft measurements where 

high spatial resolution is desired. The manufacturer provided several customizations to 

the monitor including removing all exterior switches and ports and placing them on the 

instrument’s mother board, mountain the instrument in a Pelican 1510 case. (Pelican Inc, 

Torrance, CA) The 1510 Pelican case is designed to fit under passenger airline seats. 

All interior surfaces of the pelican case were treated with anti-static paint. In flight the 

ozone monitor was powered by a Bescor NMH54, (Bescor Video Accessories Ltd, 

Farmingdale, NY) 4.5 AmpHr Nickel Metal Hydride rechargeable battery. Each battery 

provided 7 hours of continuous operation. The ozone monitor battery also powered the 

Setra pressure transducer and the Crossbow Tilt sensor.

Specifications of Model 205 Ozone Monitor, 2B Technologies, Boulder Colorado

Measurement Principle UV Absorption at 254 nm; Dual Beam

Linear Dynamic Range 1.0 ppb to 250 ppm

Resolution 0.1 ppb

Precision (1σ; rms noise) Greater of 1.0 ppb or 2% of reading

Accuracy Greater of 1.0 ppb or 2% of reading

Limit of Detection (2σ) 2.0 ppb

NIST-Traceable Calibration Yes

Measurement Interval 2 s (Data averaging options: 2 s; 10 s, 1 min, 5 min, 1 hr)

Flow Rate (nominal) ~1.8 Liter/min

Flow Rate Requirement >1.2 L/min

Baseline Drift <1 ppb/day, <3 ppb/year

Sensitivity Drift <1%/day, <3%/year

Measurement Time, 

Frequency 2 s, 0.5 Hz

Response Time, 100% of 

Step Change 4 s, 2 points

Corrections Temperature and Pressure

Operating Temperature 

Range 

0 to 50 °C; -20 to 50 °C with low temperature modifications (rotary 

vane pump and lamp heater)

Operating Altitude Range ~0-30 km (~30-1000 mbar)

CO2, CO, Temperature, RH and Pressure

CO2, CO, Temperature, RH and Pressure were measured using a Q-Trak Model 7565 

Indoor Air Quality Meter with a Model 982 probe (TSI Incorporated, Shoreview, Mn). 

This unit was selected because of its compact design and its small power requirement 4 

AA alkaline batteries per nine hours of continuous operation. The specifications of each 
Appendix A Page 4

individual sensors were comparable to the specifications of stand alone units for each 

parameter. The Probe was mounted on the top of the 1510 pelican case and the Q-trak 

unit was mounted on the inside cover. The Q-track unit was separated from the ozone 

monitor with 1 inch thick antistatic foam.

Q-TRAK Model 7565 (Model 982 Probe) Specifications

Carbon Monoxide (Probe Model 982) Sensor Type Electro-chemical

Range 0 to 500 ppm

Accuracy 1 ±3% of reading or 3 ppm, whichever is greater

Resolution 0.1 ppm

Response Time <60 seconds to 90% step change

Carbon Dioxide (Probe Model 982)

Sensor Type Dual-wavelength NDIR (non-dispersive infrared)

Range 0 to 5,000 ppm

Accuracy 2 ±3.0% of reading or ±50 ppm, whichever is greater

Resolution 1 ppm

Response Time 20 seconds

Temperature (Probe Model 982)

Sensor Type Thermistor

Range 32 to 140°F (0 to 60°C)

Accuracy ±1.0°F (0.6°C)

Resolution 0.1°F (0.1°C)

Response Time 

30 seconds (90% of final value, air velocity at 400 

ft/min [2 m/s])

Relative Humidity (Probe Model 982)

Sensor Type Thin-film capacitive

Range 0 to 95% RH

Accuracy 3 ±3% RH

Resolution 0.1% RH

Response Time 20 seconds (for 63% of final value)

Barometric Pressure

Range 20.36 to 36.648 in. Hg

(517.15 to 930.87 mm Hg) ±2% of reading

Accuracy 

Operating Temperature 40 to 113°F (5 to 45°C)

Storage Temperature -4 to 146°F (-20 to 60°C)

Ultrafine Particles

The Model 3781 Water-based Condensation Particle Counter (WCPC) (TSI Incorporated, 

Shoreview, MN) detects airborne particles down to 6 nm in diameter. Using single 

particle detection with live-time coincidence correction, the 3781 covers a wide particle 

concentration range up to 5x105particles/cm3 . The WCPC uses water vapor* to enlarge 

particles for easy detection by an optical detector. It provides fast response to rapid 

changes in aerosol concentration. CPCs operate on the principle of enlarging small 

particles using a condensation technique to a size that is large enough to be detected 

optically. The Model 3781 brings the convenience of using water to measure 

submicrometer aerosol particles. Using a patented technique,( Technology from Aerosol 

Dynamics, Inc., United States Patent Number 6,712,881), an aerosol sample is drawn 

continuously through a cooled saturator and then into a heated condenser where water 
Appendix A Page 5

vapor diffuses into the sample stream. Water diffuses to the centerline of the condenser 

faster than heat is transferred from the warm walls, producing super saturated conditions. 

Particles that are present in the sample stream (and larger than the minimum activation 

size) serve as condensation sites for the water vapor. Once condensation begins, particles 

grow quickly into larger water droplets and pass through an optical detector, where they 

are counted easily. The single-path sample flow design allows for precise, pressurecorrected flow control. An additional 0.48 L/min transport flow reduces particle diffusion 

losses at the sample inlet. A transport bypass lever allows measurement of aerosol flow 

rate directly at the sample inlet. The CPC was powered by a 10 Amp Hr Powerizer (AA 

Portable Power Corp, Redmond, CA). Each battery provided for 5 hours of continuous 

operation.

3781 Condensation Particle Counter Specifications

Min. Detectable Particle (D50) 6 nm, verified with DMA-classified sucrose particles

Max. Detectable Particle >3 μm

Particle Concentration Range

0 to 5×105 particles/cm3, single particle counting with 

continuous live-time coincidence correction

Particle Concentration Accuracy ±10% at 5 × 105 particles/cm3

Response Time <2 sec to 95% in response to concentration step change

Aerosol Flow Rate 0.12 ±0.012 L/min

Inlet Flow Rate 0.6 ± 0.12 L/min

False Background Counts <0.01 particle/cm3, 1-hour average

Aerosol Medium Air only, 10 to 35°C (50 to 95°F)

Ambient Temperature Range 10 to 35°C (50 to 95°F)

Ambient Humidity Range 0 to 90% RH, noncondensing

Inlet Pressure Operation (Absolute) 50 to 110 kPa (0.5 to 1.1 atm)

Inlet Pressure (Gauge) 0 to -2.5 kPa (0 to -10 in. water)

Condensing Liquid Water (distilled water recommended)

Water System

Internal reservoir for up to 2-hour operation, external 250 

ml bottle for up to 1 Week operation

Filling Method

Reservoir fed by gravity from external bottle via fill 

valve, controlled by float switch

Water Consumption 250 ml/week

PM2.5

The SIDEPAK AM510 Personal Aerosol (TSI Incorporated, Shoreview, MN) is a laser 

photometer. It is compact and quiet which is ideal for the limited space aboard aircraft. 

The flow rate was set to 800 cc/min and a Harvard Mini-PEM was used as PM2.5 a size 

selective inlet. The sidepak is powered by 6 AA Alkaline batteries, which provided 10 

hours of continuous operation.

SIDEPAK AM510 Personal Aerosol Monitor Specifications

Sensor Type 90° light scattering, 670 nm laser diode

Aerosol Concentration 

Range `

0.001 to 20 mg/m3(calibrated to respirable fraction of ISO 12103-1, A1 test 

dust)

Particle Size Range 0.1 to 10 micrometer (μm)

Minimum Resolution 0.001 mg/m3

Zero stability ±0.001 mg/m3 over 24 hours using 10-second time-constant

Temperature Coefficient 

Approximately +0.0005 mg/m3per °C (for variations from temperature at 

which instrument was last zeroed)
Appendix A Page 6

Flow Rate Range User-adjustable, 0.7 to 1.8 liters/min (L/min)

Operating Range 0 to 50°C (32 to 120°F)

Storage Range -20 to 60°C (-4 to 140°F)

Inclinometer/Tilt Sensor

To measure pitch and roll we used the CXTA02 (Crossbow Technologies, Milpitas, CA) 

dual axis analog inclinometer design centers on a highly stable silicon micromachined 

capacitive inclination sensor element. The CXTA series is fully signal conditioned with a 

high level analog output(s), and optional analog temperature output. One reading was 

collected every two seconds. The damping constant of the inclinometer was chosen to 

respond adequately to movements of aircraft associated with turbulence, but not to higher 

frequency noise. The two-axis, solid state CXTLA02 by Crossbow Technology is 

compact (1" x 2" x 1"), lightweight (~0.1 lb), and will measure pitch and roll angles as 

large as ± 20°. 

CXTA02 Inclinometer Specifications

Parameter Units

Linear Angular Range ± 20°

Full Angular Range ±75°

Angular Resolution 0.05° rms

Sensitivity 35 mV/°

Scale Factor Drift 0.01 %/°C

Zero Angle Voltage 2.5±0.15 Volts

Zero Angle Drift 1 mV/°C

Zero Angle Drift 0.2 °/°C

Non-Linearity 0.4°

Bandwidth 125 Hz

Settling Time 0.2 Sec.

Alignment ± 1°

Crossaxis Sensitivity 5 %

Storage Temperature -55 to 85 °C

Operating Temperature -40 to 85 °C

Vibration 10 Grms

Shock 2000 G

Supply Voltage "8-30" VDC

Current 8 mA

Sound Level

The Quest Model is a precision Class/Type 1 sound level meter. It is RFI-shielded. . Its 

dynamic range is large (30-140 dB), covers the levels expected in typical aircraft 

environment. The instrument is lightweight (~0.7 lbs), runs off a 9V battery (10 hours of 

continuous operation), and has excellent precision (1 dB) and accuracy (±0.5 dB).
Appendix A Page 7

Quest Model 1100 Sound Level Meter Specifications

Measurement Range 30 to 140 dBA

40 to 140 dBC

Microphone

Size 13.5 mm

Type Electret

Preamp Optional

Internal Filters A,C

Response Time Constants F, S

Exchange Rates N/A

Outputs AC/DC

Temperature Range

Operating -10°C to 50°C

Storage -20°C to 60°C

Standards

Class/Type 1

ANSI S1.4 Yes

ANSI S1.43 N/A

IEC 60651 Yes

IEC 60804 N/A

IEC 61672-1 Yes

CE Mark Yes

ETL Intrinsic Safety Approval Yes

CSA Intrinsic Safety Approval Yes

Pressure (Secondary Sensor)

A Setra Model 278 pressure transducer (Setra Systems Inc, Boxborough, MA) served as a 

secondary pressure sensor.

Model 278 Specifications

Full Scale Pressure Output 2.5 VDC 

Zero Pressure Output 0 VDC

Accuracy (RSS Method) ±0.25% Full Scale

Type of Pressure Absolute

Pressure Range (hPa/mb) 500 to 1100 

Temperature @ Accuracy (hPa/mb)

+20oC (+68oF) ±0.6 

0 to +40oC (+32o to +104oF) ±1.2 

-20o to +50oC (-4o to +122oF) ±2.0 

-40o to +60oC (-40o to +140oF) ±2.5 

Thermal Effects Temperature

Operating °C (°F) -40 to +60 (-40 to +140)

Storage °C (°F) -60 to +120 (-76 to +248)

Media Non-condensing air or gas 
Appendix A Page 8

Integrated Samples

Volatile Organic Compounds (VOCs) Ozone Reaction By-products and Carbonyls

Methods

For airline A, VOC samples were collected using Entech Instruments, 400 ml silonite 

coated evacuated canisters. For airlines B and C, VOC samples were collected on stainless 

steel, multi-bed thermal desorption tubes (TDTs) from Supelco, triple sorbent tube multibed TDTs with 200 mg of Carbopack B, 230 mg of Carbopack X and 170 mg of Carboxen 

1001 (Supelco/Perkin-Elmer), following USEPA Compendium Method TO-17: 

“Determination of Volatile Organic Compounds in Ambient Air Using Active Sampling 

onto Sorbent Tubes”. Ozone reaction by products were collected on stainless steel, thermal 

desorption tubes (TDTs) from Supelco, packed with 500 mg Tenax A. The tubes were 

conditioned prior to their use, as described in TO-17, by heating the tubes at 350°C for 2 

hours and passing 50 mL/min of pure helium gas through them. In addition, used tubes 

were re-conditioned for 15 minutes after analysis before returning to the field. Flows were 

collected at 27 cc/min (sd 6.2 cc/min) using a battery powered Omni Pump (BGI, 

Waltham, Ma). Final volumes were corrected to STP. 

VOC samples were analyzed on Perkin-Elmer Automatic Thermal Desorber (ATD) 

interfaced to a Hewlett Packard GC/MSD using EPA method TO-17. The ATD transfer 

line connects directly to the J&W Scientific DB-1 column inside the GC oven. Dry purge 

and internal standard (IS) addition was accomplished in one step. Sample tubes were placed 

on a spiking device (tubing connected to an ultra high purity nitrogen tank with fitting for 

the tube) with carrier flow of 75 mL/min. A vapor phase IS was injected into the device 

and the tube was kept in place for 5-30 minutes. The vapor phase IS was made from liquid 

standards in solution (usually methanol) of a known concentration that are injected as a 

known volume into a 2 L static dilution bottle. A volume of vapor was drawn up with a 

gas-tight syringe and injected into the injector-port/spiking device with flow onto the 

sample tube. Initial calibration standards were prepared the same way. Drawing different 

volumes yields different masses and thus the different levels of calibration. 

For airline B, Ozone reaction by product samples were analyzed on Perkin-Elmer 

Automatic Thermal Desorber (ATD) interfaced to a Hewlett Packard GC/MSD using EPA 

method TO-17. Flows were collected at 35.5 cc/min (sd 8.8 cc/min) using a battery 

powered Omni Pump (BGI, Waltham, Ma). Final volumes were corrected to STP. The 

ATD transfer line connects directly to the J&W Scientific DB-1 column inside the GC 

oven. Dry purge was accomplished in one step. Sample tubes were placed on a device 

(tubing connected to an ultra high purity nitrogen tank with fitting for the tube) with carrier 

flow of 75 mL/min. The tube was kept in place for 5-30 minutes. Calibration standards 

were made from liquid standards in solution (usually methanol) of a known concentration 

that are directly injected as a known volume onto clean TDTs. Injecting different volumes 

yields different masses and thus the different levels of calibration. 
Appendix A Page 9

For airlines A, B and C, Formaldehyde, acetaldehyde, acetone and propionaldehyde were 

sampled actively using a commercially available sampler 2,4-dinitrophenylhydrazine 

(DPNH) coated silica cartridges (Waters Associates, Milford, MA). Samples were 

collected at 71.2 cc/min (sd 8.8 cc/min) and stored at –4°C. The samples were prepared by 

desorbing the DNPH derivative from the substrate with 5 mL of acetonitrile. This was 

done in a vacuum chamber with 12 sample positions, each fitted with a valve to control the 

extractant flow rate to approximately 1 mL per minute. The extracts were collected 

directly into 5 mL volumetric flasks or graduated test tubes. After removing the vacuum 

the samples were diluted to 5 mL with acetonitrile. Aliquots were pipetted into special 1 

mL amber vials (Whatman mini-prep vials with 0.45 μm filter) for chemical analysis.

Formaldehyde, acetaldehyde, acetone and propionaldehyde samples were analyzed by High 

Performance Liquid Chromatography (HPLC) with ultraviolet detection using Agilent 1100 

series HPLC equipped with a quaternary pumping system, a degassing unit, a 100-position 

autosampler, a thermostatted column compartment and a UV-visible variable wavelength 

detector (VWD) set at 360 nm. The mobile phase was a mixture of water, acetonitrile, and 

tetrahydrofuran at a flow rate of 1.5 mL/min. A 20 microliter sample was injected and the 

compounds including the DNPH derivatives were separated in less than 30 minutes with a 

gradient on a 150 mm x 3.9 mm ID Waters reverse-phase Nova-Pak C10 column. The data 

were processed automatically with the Agilent Chemstation© Software.

Detection limits were calculated by the higher value of either three times the standard 

deviation for each target compound of the field blanks or the method detection limit for 

each target compound of the instrument as determined by the Method TO-17, section 14.2. 

Method Detection Limit. 

TCP

For airlines B and C, A sampling manifold split the flows from the pumps to obtain the 

target flow for each sample type. Flows for each sample were measured using a TSI model 

4146 volumetric flow meter and recorded at sample set up and take down and periodically 

checked during the flight using a volumetric flow meter (Shoreview, Mn). Tricresyl 

Phosphate (TCP) samples were collected on Whatman QMA 37 mm quartz filters at flow 

rates of 1.8 to 4.5 liters per minute (Lpm). Filters were used as received. 

Extraction

Extraction was accomplished by sonication. Each Whatman QMA 37mm quartz filters 

was placed inside a clean 8 mL vial and 5-6 mL dichloromethane (DCM) was added to 

each vial to ensure complete coverage of the filter. Vials were sealed with a Teflon-lined 

screw cap and sonicated for 30 minutes. Water in the sonication bath was kept chilled to 

approximately 4 °C with “blue-ice” packs. Each extract was transferred by Pasteur 

pipette to a clean 8 mL vial. The 5-6 mL extracts were placed under a gentle stream of 

nitrogen and reduced to dryness. A syringe was used to add 500 μL of Toluene to each 

vial, which was vortexed to ensure that Toluene rinsed the sides of the vial adequately. 

An aliquot was withdrawn and placed into an insert in the analytical vial to be placed on 

the GC/MS instrument.
Appendix A Page 10

Matrix Spiking

Two procedural blanks (PB) (unspiked clean filters) and six matrix spikes (spike of the 

target analyte) were analyzed The six matrix spikes were further divided into three each 

of low and high levels. The spike solution had a concentration of 100.0 ng/mL for each 

TCP isomer: tri-o-cresyl phosphate, tri-m-cresyl phosphate, and tri-p-cresyl phosphate

(Accustandard, New Haven, CT). Spike volumes were 5.0 μl and 50.0μl for the low and 

high spikes, respectively. This yielded low spike amounts of 0.50 ng/filter and high spike 

amounts of 5.0 ng/filter. 

Analysis

Samples are analyzed on an Agilent 6890N Gas Chromatograph with an attached 5975 

Mass Spectrometer. The GC/MS is operated in Selective Ion Monitoring (SIM) mode 

with Electron Impact Ionization (EI). Separation is by capillary column, an HP-5MS from 

Agilent. Column dimensions are 30m x 250 um (id) x 0.25 um (film thickness). A fourpoint calibration curve was established using standards at 0, 2, 4, and 10 ng/mL. 

Detection limits were calculated by using the higher value of either three times the standard 

deviation for each target compound of the field blanks or the method detection limit for each 

target compound of the instrument. The method of detection limit is calculated by analyzing nine

replicate spiked samples (1 ng) and multiplying the standard deviation of the replicate samples by 

the appropriate Students’ t-value at the 99% confidence level (2.90 for nine replicates).

SVOC

Flows for SVOCs averaged from 3.6 LPM (0.46) LPM (depending on flow requirements 

of other sample types collected concurrently). Flows for each sample were measured 

using a TSI model 4146 volumetric flow meter (Shoreview, Mn) and recorded at sample 

set up and take down and periodically checked during the flight. Samples were collected 

on either SKC model 226-143 glass sorbent tubes, 22 mm by 100 mm, packaged by SKC 

with 1.5 grams of XAD2 sandwiched between two 3.0 cm puf plugs or URG model 

URG-2000-30PUF-1 glass sorbet tubes, 28 mm by 137 mm, packed by Battelle 

Laboratory with 5 grams of XAD2 sandwiched between two 1.9 cm puf plugs. The 

sorbent tubes were shipped and maintained chilled after field spiking with deuterated 

surrogates until sample extraction. 

Soxhlet extraction with dichloromethane (DCM), and concentration to 0.1 mL prior to 

analysis in the electron impact (El) GC/MS multiple ion detection mode for the majority 

of the analytes, followed by negative chemical ionization (NCI) GC/MS of the same 

extract for the selected brominated compounds. 
APPENDIX B

In-Flight/Onboard Monitoring: ACER’s Component for 

ASHRAE 1262, Part 2

Comparisons of Volatile Organic Compounds
Appendix B Page 2

Appendix B provides, for comparative purposes, indoor data on VOCs collected in three 

studies. The authors of this FAA technical report were involved with each of these studies. 

First, Table B-1 summarizes the VOC compounds measured in cabin air and the percent 

of samples with concentrations above the limit of detection (LOD). 

Table B-1. VOC compounds measured by airline and number of samples and percentage of samples 

above the LOD. Airline A had a total of 21 samples, airline B had a total of 35 samples, and airline 

C had a total of 31 samples.

airline A airline B airline C

N >LOD % >LOD N >LOD % >LOD N >LOD % >LOD

1,3-butadiene 1 5% 12 34% 8 24%

methyl tert-butyl ether 6 29% 7 20% 8 24%

Benzene 20 95% 26 74% 4 12%

Toluene 21 100% 33 94% 28 82%

Ethylbenzene 20 95% 15 43% 24 71%

m&p-xylene 21 100% 20 57% 27 79%

o-xylene 21 100% 11 31% 23 68%

methylene chloride 16 76% 25 71% 12 35%

Chloroform 15 71% 3 9% 14 41%

1,1,1-trichloroethane 12 57% 5 14% 11 32%

carbon tetrachloride 20 95% 32 91% 29 85%

Trichloroethene 17 81% 17 49% 7 21%

cis-1,3-dichloropropene 0 0% 0 0% 1 3%

trans-1,3-dichloropropene 0 0%

Tetrachloroethene 21 100% 29 83% 31 91%

1,4-dichlorobenzene 21 100% 5 14% 13 38%

Acrolein 19 90% 19 56%

Acetone 21 100%

2-butanone 21 100% 26 76%

Ethanol 21 100% 15 44%

ethyl acetate 21 100% 20 59%

Hexane 18 86% 27 77% 1 3%

Isoprene 21 100% 18 53%

isopropyl alcohol 20 95% 31 91%

Styrene 21 100% 14 40% 11 32%

2-Methylpentane 30 86% 2 6%

2-Methylhexane 10 29% 11 32%

2,3-Dimethylpentane 8 23% 14 41%

3-Methylhexane 9 26% 13 38%

2,2,4-Trimethylpentane 25 71% 28 82%

Methylcyclohexane 9 26% 22 65%

Propylene 20 95%

methyl bromide 6 29%

Methyl methacrylate 2 10%

1,2,4-trimethylbenzene 21 100%

Dichlorodifluoromethane 21 100%

Tetrahydrofuran 6 29%
Appendix B Page 3

airline A airline B airline C

N >LOD % >LOD N >LOD % >LOD N >LOD % >LOD

Cyclohexane 20 95%

methyl chloride 20 95%

vinyl acetate 17 81%

carbon disulfide 19 90%

Heptanes 16 76%

Trichlorofluoromethane 21 100%

1,3,5-trimethylbenzene 21 100%

2-hexanone 11 52%

trans-1,2-dichloroethene 10 48%

1,3-dichlorobenzene 10 48%

methyl isobutyl ketone 12 57%

4-ethyl toluene 21 100%

Chlorobenzene 9 43%

ethyl chloride 2 10%

1,2,4-trichlorobenzene 11 52%

1,1,2-trichlorethane 1 5%

1,2-dichlorobenzene 9 43%

1,1,2,2-tetrachloroethane 2 10%

1,1,2-trichloro-1,2,2-trifluoroethane 21 100%

Bromoform 5 24%

benzyl chloride 5 24%

Hexachlorobutadiene 6 29%

1,2-dichloroethane 4 19%

1,2-dichlorotetrafluoroethane 15 71%

Dibromochloromethane 2 10%

The EPA Building Assessment Survey Evaluation (BASE) study was conducted to assess 

“background” conditions in non-complaint office buildings (buildings not reporting sick building 

syndrome) in the U.S. Using a sample selection scheme to represent probabilities for 

participation, owners of 100 buildings agreed to participate. All of the buildings were located in 

urban areas. The comprehensive evaluation of the HVAC systems along with extensive 

measurements of air quality parameters comprised the environmental component of BASE. In 

addition, over 5000 surveys were collected from building occupants reporting perceptions on 

environmental conditions as well as their health symptoms. We used the median VOC values 

from BASE to compare to the median values of compounds detected in each of the three airlines. 

As shown in Table B-2, the majority of VOC compounds had median values in buildings

similar to or higher than what has been found in the cabin. For more details on BASE see 

Brightman et al. (2008) Indoor Air 18:335-345.
Appendix B Page 4

Table B-2. Comparison of median EPA BASE VOC (ng/m3) measurements with VOC 

measurements in all three airlines.

BASE airline airline airline Ratio Ratio Ratio

Median A B C BASE/A BASE/B BASE/C

Median Median Median

Non-chlorinated

1,3-butadiene 2100 0 618 534 3.4 3.9

methyl tert-butyl ether 1400 0 35 19 40.0 73.7

benzene 3500 876 548 116 4 6.4 30.2

toluene 9400 2783 2846 10105 3.4 3.3 0.9

ethylbenzene 1700 187 230 418 9.1 7.4 4.1

m&p-xylene 5700 333 956 1120 17.1 6.0 5.1

o-xylene 2200 163 291 409 13.5 7.6 5.4

Chlorinated

methylene chloride 7700 45641 2842 0.2 2.7

chloroform 440 35 138 95 12.6 3.2 4.6

1,1,1-trichloroethane 3600 10 63 31 360 57.1 116.1

carbon tetrachloride 900 28 649 639 32.1 1.4 1.4

trichloroethene 370 21 324 132 17.6 1.1 2.8

cis-1,3-

dichloropropene 1500 0 0 0

trans-1,3-

dichloropropene 850 0

tetrachloroethene 1800 619 1166 10670 2.9 1.5 0.2

1,4-dichlorobenzene 700 187 322 307 3.7 2.2 2.3

Other

acetone 33000 23563 1.4

2-butanone 2600 2154 1356 1.2 1.9

ethanol 43000 1433770 0

ethyl acetate 2000 1751 16132 1.1 0.1

hexane 2400 262 68360 0 9.2 0.0

isopropyl alcohol 22000 3095 6312 7.1 3.5

styrene 920 161 369 416 5.7 2.5 2.2

The cabin air VOCs were also compared to VOCs reported in residential studies 

conducted in Los Angeles, as part of the Toxic Exposure Assessment: Columbia-Harvard 

(TEACH), and in Boston, in the Boston Exposure Assessment in Microenvironments (BEAM) 

study. These studies collected VOCs with sorbent tubes and analyzed by thermal desorption 

with GC/MS. The lab and methods were the same as those used for samples from airlines B and 

C in this study. 
Appendix B Page 5

In Table B-3, distributional information on VOCs from the TEACH and BEAM studies 

were compared to each of the airlines. The figures within the body of the report present 

graphically some of the data contained in this stable. Specific compounds have been found in 

higher concentrations in the cabin air. It should be noted that there are differences across airlines 

as well as within airline groupings. For example, while the median value for benzene in cabin air 

is comparable to BEAM data, a few flights had substantially higher values, one for airline B and 

one for airline C. Toluene, ethylbenzene, o-xylene, 1,3-budadiene, and styrene all showed a 

pattern where a few flights had values substantially higher than what might be expected in 

homes. A few chlorinated hydrocarbons also had this pattern. These concentrations are 

remarkable considering the high ventilation rates in airplanes compared to residences and the 

assumed low background levels in ambient air at cruise altitudes.

More details about the TEACH are reported by Sax et al. (2004) Journal of Exposure 

Analysis and Enviornmental Epidemiology, 14:S95-S109, and by Dodson et al. (2007) 

Environmental Science & Technology, 41(3):259-270 for the BEAM study.

Table B-3. Comparison of cabin VOC measurements (μg/m3) with measurements made in the 

BEAM and Teach studies.

min 25th median 75th max

Benzene TEACH 0.36 1.47 2.13 3.28 8.35

BEAM 0.02 0.41 0.75 1.16 3.59

airline A 0.00 0.54 0.88 1.18 3.29

airline B 0.00 0.26 0.55 1.47 20.07

airline C 0.00 0.00 0.12 3.01 62.34

Toluene TEACH 1.27 8.23 10.78 15.44 54.66

BEAM 0.18 1.09 2.00 2.97 5.61

airline A 1.01 1.89 2.78 4.39 30.03

airline B 0.46 1.93 2.85 6.43 115.38

airline C 0.12 6.08 10.10 15.74 132.93

Ethylbenzene TEACH 0.02 1.60 2.35 2.97 18.68

BEAM 0.05 0.23 0.36 0.53 1.87

airline A 0.00 0.12 0.19 0.28 0.57

airline B 0.06 0.13 0.23 0.50 13.45

airline C 0.00 0.27 0.42 0.65 3.86

m/p Xylene TEACH 0.16 5.73 8.46 10.99 26.00

BEAM 0.13 0.65 1.12 1.61 6.63

airline A 0.15 0.22 0.33 0.52 0.71

airline B 0.21 0.49 0.96 1.90 28.67

airline C 0.00 0.76 1.12 2.38 9.39

o Xylene TEACH 0.14 2.19 3.05 4.12 32.05

BEAM 0.06 0.25 0.40 0.56 2.34

airline A 0.07 0.10 0.16 0.24 0.42

airline B 0.00 0.13 0.29 0.48 14.17

airline C 0.00 0.27 0.41 0.76 3.44
Appendix B Page 6

min 25th median 75th max

1,3-butadiene TEACH 0.03 0.03 0.03 0.03 1.70

BEAM 0.03 0.15 0.18 0.28 2.81

airline A 0.00 0.00 0.00 0.00 0.04

airline B 0.00 0.13 0.62 6.17 212.71

airline C 0.00 0.01 0.53 1.76 50.41

MTBE TEACH 0.03 10.15 13.93 18.97 44.79

BEAM 0.14 0.57 1.05 1.56 5.81

airline A 0.00 0.00 0.00 0.01 0.09

airline B 0.00 0.01 0.03 0.20 16.16

airline C 0.00 0.00 0.02 0.49 3.66

Styrene TEACH 0.14 0.38 0.61 0.80 4.31

BEAM 0.00 0.06 0.09 0.13 0.33

airline A 0.04 0.08 0.16 0.23 0.50

airline B 0.11 0.27 0.37 0.62 3.39

airline C 0.00 0.15 0.42 0.90 12.08

Chloroform TEACH 0.03 0.06 0.07 0.14 0.98

BEAM 0.02 0.03 0.04 0.06 1.13

airline A 0.00 0.00 0.04 0.10 0.53

airline B 0.02 0.08 0.14 0.27 2.09

airline C 0.00 0.00 0.10 0.46 1.96

Trichloroethene TEACH 0.03 0.07 0.10 0.15 0.76

BEAM 0.02 0.02 0.02 0.09 4.06

airline A 0.00 0.01 0.02 0.03 0.65

airline B 0.00 0.07 0.32 1.40 29.45

airline C 0.00 0.00 0.13 2.33 41.29

Tetrachloroethene TEACH 0.08 1.03 1.59 1.94 4.28

BEAM 0.03 0.15 0.24 0.37 7.56

airline A 0.05 0.27 0.62 0.92 1.93

airline B 0.07 0.81 1.17 2.60 10.01

airline C 1.18 3.44 10.67 13.32 123.03

Dichlorobenzene_14 TEACH 0.32 0.91 1.55 3.16 197.04

BEAM 0.02 0.07 0.13 0.29 3.28

airline A 0.04 0.12 0.19 0.28 0.70

airline B 0.05 0.17 0.32 0.59 2.42

airline C 0.00 0.04 0.31 0.77 12.74