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Aircraft cabin CO2 and Oxygen measurements (C) Daniel FriedmanIn-Flight Carbon Dioxide CO2 & Oxygen Levels on Commercial Aircraft

  • AIR QUALITY on COMMERCIAL AIRCRAFT - CONTENTS: an informal study of carbon dioxide level variation during in-flight conditions on long commercial aircraft found little variation by altitude nor flight duration. Some consumers speculated to the author that poor air quality, reduced oxygen, or elevated CO2 might explain dizziness or respiratory distress experienced by some airline passengers.
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Commercial aircraft air quality:

Airplane cabin IAQ, fresh air ventilation, and oxygen and carbon dioxide levels were examined by measuring CO2 and O2 levels during long flights.

This article reports the results of a limited study of the variation in oxygen levels and carbon dioxide levels during long commercial air flights in 2014. This study was made by performed by using safe, simple and accurate gas detection tube analysis to measure both oxygen and carbon dioxide levels at various points in fight.

Results suggest that the levels of these two gases in the aircraft cabin indeed varied, but not by much during long commercial airline flights at typical high altitudes.



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Levels of Carbon (CO2) Dioxide & Oxygen (O2) & Ozone During Flight

Airborne debris indoors (C) Daniel Friedman Daniel Friedman - [in process - March 2015]

Waters et al (2002) reported "Carbon dioxide exposures were highest on shorter and high-occupancy flights, aircraft with greater recirculated-to-fresh-air ratio, and narrow -bodied aircraft. In general contaminant levels were low compared to standards. Carbon dioxide levels indicated lower ventilation rates per occupant than most other indoor environments."

[Click to enlarge any image]

Those authors measured aircraft cabin CO2 at 515 - 4902 ppm and reported that CO2 levels were likely to be elevated in aircraft cabins on short flights in full or nearly-full aircraft.

They also provide a succinct description of how cabin air is supplied to airline passengers:

Engine compressor bleed air is pre-conditioned, sent to the air conditioning packs, and delivered to the cabin through a manifold that permits mixing with recirculated cabin air.

Outside air is not filtered but the recirculation system incorporates air filtration; types and efficiency of filters vary by aircraft.

Recirculation maintains air supply rate and minimizes use of more costly bleed air.  - Waters et al (2002)

Aircraft cabin air quality (C) InspectAPedia

I previously studied the rate of change of indoor CO2 in a crowded synagogue that had no functional fresh air ventilation system. During the religious service the CO2 level indoors increased significantly, possibly shifting an explanation of the apparent drowsiness of the congregants from Rabbi Arnold's sermon to the building's indoor air quality. One might ask if similarly the CO2 might increase in the cabin of a crowded airplane during a long flight - a different hypothesis than that offered by Waters et als and one that investigates the current (2014) ventilation rate on commercial aircraft.

I have received anecdotal reports of a air passengers experiencing dizziness and fainting during long air flights (Lukacher 2014) , typically transcontinental travel.

Airborne debris indoors (C) Daniel Friedman

While altitude has been discussed regarding air passenger comfort anecdotal reports speculated on changes in either oxygen level or carbon dioxide level as possible contributors to the experiences of these passengers.

While altitude or other explanations for fainting and dizziness during long air flights may pertain, I wanted to investigate the cabin air quality, specifically oxygen and carbon dioxide, and to compare those results with air passenger speculations about oxygen and CO2 levels in aircraft during long flights.

Previously I have collected airborne particle samples using an adhesive air sampling cassette in order to examine in-cabin airborne particulates in the air stream from the cabin's ovehead air supply. Particulate levels down to 1u were very low: I did not find much of interest. Particulate filtration on modem aircraft appears to be quite effective at least for larger particles such as common dust, pollen, and mold spores. Very small particles such as bacteria and viruses were not studied by the author but were studied by some of the authors cited below.

Oxygen & carbon dioxide sampling results inside a commercial aircraft, in-flight (C) Daniel Friedman

In 2014, on a series of long commecial air flights including trips between Mexico and the U.S. and between the U.S. and New Zealand, the author used a simple air sampling pump made by Drager to collect periodic samples of the level of both carbon dioxide and oxygen in the passenger cabin of the commercial aircraft during those flights.

At left are the oxygen sampling tube (above) showing about 11.25% concentration of oxygen in the aircraft's cabin, and a carbon dioxide gas sampling tube after 20 pump strokes showing nearly 1500 ppm - a number that must be divided by two to obtain the actual concentration of about 750 ppm of CO2 for this measurement.

The data recorded included the total flight time, altitude, aircraft model and number of passengers aboard, along with the point in the flight by time and distance at which various samples were collected. The results are reported in the airplane cabin IAQ table below.

Table of Carbon Dioxide CO2 and Oxygen Levels Measured in Commercial Aircraft Cabins During Flight

Flight / Row / Date Carbon
Dioxide
ppm
Oxygen
%
Sample
Time
[1]
Total
Flight
Time
Altitude Aircraft / Capacity Passen-
gers + crew
% Capac. Comments
UA 1063 / r10 04.07.14[2] 400ppm   1 hr
09:30 A
4 hr 35,000 ft B737-800/900 / 145 144 100% EWR->MEX, est. Cabin Temp 70F,Tube 100/a, 10 pump strokes
400   1 hr
5 min
35,000 ft Control. Cabin air samples collected @ lap height
630   3 hr
12:30 P
35,000 ft 20 pump strokes for precision
 
UA 718 / r8 /
03.09.14
600
750[3]
11.5%
13%
0.00
02:55 P
2 h 40m Ground A320 / 120-150 90 66% MEX->SFO Control, prior to takeoff
600
625[3]
11.2%
12.5%
05:50 P 34,000 ft 66% MEX->SFO
 
NZ 7 / r14 /
03.09.14
600
700[3]
12.8% 16:00 NZT 12 h 32,000 ft
9753 m
B747 400 / 416-524
332 79% SFO->AKL dep , climbing, 20 min. into flight. Total distance 10,618 Km
650
900[3]
12.25% 20:34 NZT 33,999 ft
10,363m
8 hrs from destination, outside temp -42C
600
700[3]
12%
11.75%[3]
01:00 NZT 35,997 ft
10,972m
over PagoPago, outside temp -46C
 
NZ 531 /r10/
05.10.14
                AKL->CCH
 
NZ 548 / r13/
23.10.14
  12%
11.5%[3]
20:40 NZT 1h 5m 35,000 ft
10,668m
A320   100% CCH->AKL
 
NZ 2 / r45/
23.10.14
      11h 25m 30,997 ft
9448m
B777-300 250 + crew 83%

Traveled: 5054 Km
Total distance 10,373 Km
Skycouch
Outside -46C

600
750[3]
12.25%
12.25%[3]
03:53 NZT
07:53 LAT
32,998 ft
10,058m

Over the Equator Lat 0.09S
Long: 154.10W
Outside -38C
Speed 946 KmH

800
1000[3]
12.25%

06:45 NZT
10:45 LAT

35,000 ft 10,668m Lat 17.47N
Long: 1.39.12W Outside -45C
Speed
901 KmH
Traveled:
7819 Km
Remaining
2757 Km
 
UA 274 /r22/
23.10.14
                LA->MEX
 
Pending                  
                   
                   
                   

Notes:

1. Time in minutes into the total flight time

2. Dates are given in international format dd/mm/yy

3. Second reading using same sampling tube by doubling number of pump strokes for increased precision.

4.Drager gas detection tubes used: colorimetric type. Selecting the proper detection device sensitivity range is important for obtaining accurate measurement of gases in air. I used:

  • Carbon Dioxide level measurement: Drager Rohrchen Carbon Dioxide 100/1, certified manufacturer ISO 9001. This tube is designed for measuring CO2 levels are between 100 - 3000 ppm. Ten Drager gas pump measurement strokes are used with this tube, or the operator can use 20 pump strokes and divide the resultant measurement by 2 for increased precision. Standard deviation is +/- 10-15%. The tube colour changes from white to violet on exposure to CO2. and operates at temperature ranges from 15°C to 25°C and at humidity less than or equal to 23 mg/L (corresponding to 100% RH at 25C). An atmospheric correction factor to be applied is F=1013 / actual ATM pressure.
  • Oxygen level measurement: Drager Rohrchen Oxygen 5%, certified manufacturer ISO 9001. This tube is designed for measuring the level of oxygen in air in the range of 5% to 23% by volume. One pump stroke is used to perform a measurement.

    Standard deviation is +/- 10-15%. The tube changes color from blue-black to white on exposure to oxygen and operates in the temperature range of 5°C to 50°C and at humidity from 0-40 mg/L. The literature includes a correction factor F = 1013hPa (14.692 psi) / actual atmospheric pressure - a factor that may be especially pertinent at high altitudes or in examining aircraft cabin conditions. The detector tube also has two reading scales, chosen based on which Drager sampling pump is used. Because this tube heats to as much as 100°C it should not be used where explosive gases may be present.
  • The Dräger sampling pump was leak-tested prior to use of the detection tubes by using the manufacturer's recommendations. The pump was air-flushed between measurements.
  • Draeger Safety Inc. 101 Technology Drive Pittsburgh, PA 15275-1057 USA, Tel: +1-800-858-1737 +1-412-787-2207, Website: http://www.draeger.com (their website was not functioning properly - Nov. 2014)
    Draeger Safety Inc. (Gas Detection Systems) 505 Julie Rivers Suite 150 Sugarland, TX 78478-2847 +1-800-230-5029 +1-800-375-3073. Drägerwerk AG & Co. KGaA

5. Other gas concentration in air conversions:

1 ppm CO2 = 1.8 mg CO2M3
1 mg CO2 = 0.56 ppm CO2 (at 20°C, 1013hPa)

Discussion

With additional measurement reports pending, I found in-flight cabin air quality measurements of oxygen to be relatively stable, ranging from 11.2% to 12.5%.

Typical outdoor CO2 levels are between 350-400 ppm (0.035% - 0.04%) or up to 500 ppm by some sources.

Carbon dioxide levels measured in-flight in the aircraft cabin ranged between 0.04% or 400 ppm and 0.1% or 1000 ppm to date in our studies and were measured at close to 0.5% or 5,000 ppm in earlier studies.

As indicated at CO2 HEALTH EFFECTS, occupants are unlikely to be affected or to notice CO2 levels under 2% or 20,000 ppm - a far higher number than in-flight aircraft cabin carbon dioxide levels.

Conclusions

Opinion: Perhaps to investigate or reduce air traveler complaints of dizziness or fainting we should look more closely at altitude and cabin pressures as well as other factors such as passenger hydration (drink plenty of fluids), anxiety, physical stresses before the flight (rushing, carrying bags), passenger movement & stretching during flight (avoid blood clots), the increasingly cramped seat space limitations and cramping, and aircraft cabin ozone levels.

Note: my measurements of equivalent altitude indicate that typical cabin pressures during flight give an altitude of about 7,000 feet. As I have observed simply among visitors to San Miguel de Allende, Mexico, (altitude about 6500 feet), unaccustomed people are often physically stressed at that altitude, experiencing shortness of breath and on occasion dizziness.

Opinion: An increase in respiration rate by an "out-of-breath" passenger experiencing quite understandable anxiety can exacerbate those conditions.

Bagshaw et als (2002) point out that

Commercial air carriers train their flight attendants to recognize common symptoms of distress and to respond to medical emergencies with first - aid, basic resuscitation techniques, and the use of emergency medical oxygen. ... It cannot be overemphasized that these medical kits are only for emergency use and not for routine medical care.
...
In general, ... studies have consistently revealed levels of organic substances, carbon monoxide, carbon dioxide, and airborne particles in the cabin air well below regulatory standards and below those encountered in offices, the street, or subway.

One exception is ozone, a substance found naturally in the atmosphere at altitudes where most commercial aircraft fly. It enters the cabin with outside air that is used for cabin ventilation. Ozone is a respiratory system irritant and can cause chest tightness, coughing, and shortness of breath if exposure occurs at high enough concentrations. In general, low levels have been found in aircraft cabins although, in several instances, levels were measured slightly exceeding regulatory standards. Most aircraft flying at altitudes and latitudes where high ozone concentrations are encountered now have ozone converters which break down the ozone before it reaches the cabin. - Bagshaw (2002)

Keep calm. Carry on.

Research on In-Flight Air Quality, Oxygen & Carbon Dioxide Levels & Other Factors

...


Continue reading at CARBON DIOXIDE - CO2 or select a topic from closely-related articles below, or see our complete INDEX to RELATED ARTICLES below.

Or see OXYGEN - O2 Hazards

Or see INDOOR AIR QUALITY IMPROVEMENT GUIDE or see AIR QUALITY STUDY San Miguel de Allende

Also see Drager GAS DETECTORS

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