Geoff Brundrett, Aircraft Environments, May 8th 2002


Planes are changing, becoming even more reliable and able to fly even longer distances safely. Passengers are growing rapidly in number and the holiday travel business is encouraging the widest cross sectional of people to travel, including the very young, the infirm and the very old. There appears to be little active interest in the health and comfort of the passenger apart from bland reassurances. The new medical research is either missing the plane design engineers and the travel companies or being ignored. There is little Government regulation of passenger and flight attendants.

Three topics are of growing importance .....

Deep vein thrombosis

An important study recently showed that 10% of longhaul passengers over 50 years old experienced some form of thrombosis. Many did no know. Most symptoms would disappear naturally, some needed monitoring and a few needed medical treatment. Socks, specially tensioned to match the calf, solved the problem in this study. None of those wearing the socks showed DVT symptoms. Traditional factors influencing DVT are uncomfortable seats and immobility. Death from DVT is rare but DVT is best avoided. Age, race and family genetics have an influence too. Some believe that the problem is worse at high altitude.

Seating has long been the most common complaint in charter aircraft and in economy class on scheduled airlines. Loughborough University completed an excellent study of suitable seat spacing in planes, concluding that present design would satisfy 77% of the population but much wider seats and bigger spacing were necessary. ( visit to see the report).

Meanwhile obesity is increasing. Close pitch seating makes it impossible to adopt the recommended crash position and can handicap the 90 second emergency escape time. It can also discourage passengers from moving and from sleeping properly. A recent complaint about seat pitch from a charter passenger was upheld and the the travel company's subsequent appeal turned down. The Government has since promised to require a bigger seat pitch.

Altitude sickness

This is a common problem experienced by many visitors to high altitude mountain resorts. The incidence is linked to altitude, time at that altitude and speed of ascent. Susceptibility varies widely betwen individuals. Onset usually starts after 8 hours. Modern planes gain great economy by flying at ever higher plane altitudes and can reach these heights quickly. Unfortunately the cabin pressure has to be lowered to allow for the mechanical stress of these higher altitudes.
The only public measurements on flights have indicated that within the US a third of the planes flew above the recommended cabin altitude of 8,000 ft. Twenty years ago no planes flew at such a high cabin altitude.The medical guidance favours 5,000-6,000 ft for the average passenger. At high altitudes the partial pressure of oxygen is much lower than at sea level and the oxygen saturation level in the blood falls. It falls most particularly in the elderly and those with some respiratory or blood circulation weakness. It introduces headaches and nausea which passes after some adaptation time of a few days.
High altitude workers in some countries and some high altitude hotels are using enriched oxygen to compensate for the oxygen shortage.

Ventilation rates

There has been a steady lowering of the amount of fresh air supplied to passengers over recent years. Recirculation has been introduced to maintain air movement.
The US FAA have moved more positively into cabin air quality but the CAA in Britain are still awaiting research findings. Energy costs involved are uncertain but believed to be around 1% of the fuel cost. No one is sure how little needs to be supplied.
ASHRAE TC 161 have formed and reformed their ventilation committee on aircraft and their report is now several years late. No expected date for their report is known.


The many regulatory bodies see their world as one of moving planes safely. In reality they are moving people and it is important that engineers and plane operators recognise that.

Links (not necessarily the author's views)

See ASHRAE Aircraft Air Quality Media Kit for more background information

For further opionion on Aircraft air quality see

For extensive report The Airliner Cabin Environment and the Health of Passengers and Crew (2002) see

The meeting was organised CIBSE ASHRAE Group in collaboration with IMechE Greater London Region and supported by ASHRAE and South Bank University .

Group Chairman, Tim Dwyer can be contacted at

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