The sampling strategy allowed for a series of samples to be taken at
defined points on all flights, with additional provision for samples of
any „fume events to be obtained immediately should they occur. These
additional „air quality event samples were initiated by the researcher
conducting the measurements whenever any change in air quality was
detected by the PID or ultrafine instruments, or reported by anyone on
the aircraft. The protocol was designed to yield samples of these events
that were directly comparable to the routine samples taken.
first part of the study involved monitoring on Boeing 757 cargo aircraft
and included all necessary preparatory work for these operations,
including equipment purchase, questionnaire design and protocol
development. Subsequently Parts 2 to 5 of the study utilised the
equipment and methods of Part 1 to carry out monitoring on Boeing 757,
Airbus A320/1, BAe 146 and Airbus A319 passenger aircraft respectively.
Flight crew and cabin crew (if any) were requested to complete a
post-flight questionnaire for all flights. This included questions
concerning any fumes or smells that occurred during the flight. It was
also completed by the scientist conducting the air quality measurements.
The flight staff were informed that the questionnaire was to be used in
addition to normal fume event reporting procedures and that it did not
replace them. No fume event occurred during this study which triggered
the airline's formal reporting procedures.
Sorbent tube samples
were analysed for the following target compounds: Tri-ortho cresyl
phosphate (TOCP); one of a number of TCP isomers, Other tri-cresyl
phosphate (TCP) isomers; applications include a minor component of
engine oil, Tri-butyl phosphate (TBP); applications include a component
of hydraulic fluid, Toluene, m+p- xylenes, Limonene, Tetrachloroethylene
Mean values (and percentiles) for VOC/SVOC
concentrations are presented for all data (all samples for all flights
and all flight phases), for each flight, for each flight phase, and for
each part of the study (aircraft type). For ultrafine particles, TVOCs
and CO, the number of flights (flight sectors) with levels within
specified ranges are presented. More detailed data are provided in Part
2 of this report.
Mean ultrafine particle numbers (all flight
sectors) were always in the range 1,000-100,000 particles cm-3. On five
flight sectors peak concentrations exceeded the maximum range of the
instrument (500,000 particles cm-3). Mean total VOC concentrations were
mostly below 2 ppm and a number of the short duration peak
concentrations above 10 ppm were probably due to exposure to isopropyl
alcohol vapour generated by the p-Trak instrument. Maximum CO
concentrations were mostly below 2 ppm.
The most abundant
VOC/SVOCs were generally limonene and toluene. Highest concentrations of
TBP, limonene, m+p-xylene and undecane occurred during first engine
start, while TCE concentrations were highest during the immediate
sampling period. Highest levels of TOCP, other TCPs and toluene occurred
during climb, pre-landing and take-off respectively.
A total of
30 air quality event sorbent tube samples were collected during the
study. Numbers of events were similar in Parts 1, 2, 3 and 5 of the
study, and highest in Part 4. Events were largely concentrated at engine
start and take-off, with few occurring at top of climb or during cruise.
Concentrations of target analytes during these events were not elevated
compared with the routine samples collected in each respective phase of
A total of 38 flights had fumes or smells reported by at
least one crew member or researcher in a post flight questionnaire. The
dominant smell descriptor was oil or oily, reported by 26 persons. Other
descriptors were sweet, toilet smell, exhaust, chlorine, de-icing fluid,
fuel, heated dust and human waste.
Four persons reported that
the fumes/smells caused a health effect (headache or slight headache in
all cases). Some flights had up to 3 persons reporting a smell fume and
others had only one person; a total of 60 (of 552) questionnaires
reported a smell fume. Some flights had reports of smells in more than
one phase, and in two instances the smell of human waste was reported
throughout the flight. On other flights, fumes smells were reported
during only one phase.
The European standard ‘Aircraft internal
air quality standards, criteria and determination methods (BS EN 4618:
2009) sets safety limits, health limits and comfort limits for a number
of substances, including two that were measured in this study – carbon
monoxide and toluene.
The monitoring results indicate that
concentrations of carbon monoxide did not exceed safety or health
limits. Concentrations of carbon monoxide recorded during nine flights
were equivalent to the 8h TWA (time weighted average) health limit, but
this is believed to have been due to instrument malfunction rather than
actual elevated levels of carbon monoxide. All measurements of toluene
undertaken using sorbent tubes were well below the BS standard comfort
limit of 153 mg m-3, the maximum concentration of toluene measured
during flight being 0.17 mg m-3.
In the absence of specific
cabin air standards for the other pollutants measured in this study,
reference is made to other standards and guidelines established, for
example, for domestic (home) or occupational environments.
standards/guidelines are available for TCE, TBP, TOCP, xylenes and
limonene (as well as for toluene and CO). None of these
standards/guidelines was exceeded. One short term (5 minute)
concentration of limonene occurred (during Part 3 of the study) that
exceeded a recommended long term exposure limit; however, this short
duration peak would have a small impact on longer term average
It is informative also to compare measured cabin air
concentrations with levels typically seen in domestic indoor
environments. Based on the reasonably extensive database for VOCs in
indoor air in buildings, it can be concluded that the concentrations of
toluene, limonene, xylenes, undecane and TCE in the aircraft cabin air
are of similar magnitude to those occurring in homes in developed
countries. Concentrations of CO generated by combustion sources, notably
gas cookers, are often higher than those occurring in the aircraft
For TBP and TCPs, there are few data to allow
comparison of the measured levels in aircraft cabin air with the indoor
air in buildings. There are more extensive data available on levels of
organophosphates in household dust, including studies reporting levels
of TBP, but these are of limited relevance to the present study.
It is notable that in over 95% of the cabin air samples, no
detectable amounts of TOCP or other TCPs were found. TBP was detected
more routinely, but not in the majority of samples. The highest level of
TBP recorded was 21.8 μg m-3 (overall mean 1.07 μg m-3) which exceeds
any reported domestic indoor air level. TBP levels were highest during
first engine start.
Mean concentrations of most VOCs showed a
trend, with minimum values occurring during the main phases of flight
(climb to descent) and higher values when on the ground and during
take-off. This trend was not found for limonene or the TOCP and other
Regarding the possible influence of aircraft type,
no TCPs were detected during Part 3 (A320/1 aircraft), whereas limonene
concentrations were relatively high on these flights. Other identified
differences included highest concentrations of m+p-xylene occurring in
Part 5 and lowest concentrations of toluene in Part 2.
conclusion, this study successfully completed a range of air quality
measurements during the course of 100 flights. No fume events occurred
during these flights that triggered the airline's protocols for formal
reporting of incidents. Flight and cabin crew, as well as the
investigating scientists reported a number of fume /smell events in a