Odours, Olfs & Decipols

The work of P.O. Fanger, J. Lauridsen, P. Bluyssen and G Clausen Air pollution sources in offices and assembly halls, quantified by the Olf unit addressed the question of ventilation rates and the relationship with a unit of odour intensity called the Olf. In this important work a large number of people were subjected to odour levels in a variety of naturally and mechanically ventilated buildings and air conditioned spaces. The research found that for every occupant and associated odour there may be another four to five odour equivalents (olfs) released from building materials, furnishings and the air handling system.

The Units of Odour Intensity

The contribution to the industry of the work of Professor Fanger and his team in Denmark has been immense. Not only did Professor Fanger develop his well known comfort equation, which was developed empirically and contains the many variables known to make up the comfort of people, but as well as other work also developed the concept of the units of odour - the olf and the decipol. The nature of indoor pollution is very difficult to assess because of the many indoor chemicals involved. Even for pollutants that may be detected because of their odour or irritation effect there is the issue of who should be the judge of what is acceptable. Within buildings pollutants come from many sources such as the building and furnishing materials and chemicals such as correction fluid or from equipment such as photocopiers.

Hundreds of volatile organic compounds have been identified in indoor air and most seem to be much lower than for occupational standards for industrial workers although little appears to be known of the effects of long term exposure. The sheer complexity of measuring indoor pollution raises the question of people themselves being used as the test instrument. The use of questionnaires given to building occupants for identifying and assessing problems with indoor environment has been established for some time.

The approach of using a panel of assessors to judge air quality has been advocated by Professor Fanger and has given rise to the empirical units of the olf and the decipol. One olf is defined as the air pollution produced by one 'standard' person (a standard person is also defined) and a decipol is defined as the perceived air pollution level in a space in which there is a source strength of one olf and which is ventilated at 10 litres/second with unpolluted air. The proposed European air quality standard prENV 1752 Ventilation for buildings: design criteria for the indoor environment often referred to as the Fanger Standard and at least 7 years in the making has failed to be adopted by Europe as it was not endorsed by 71% of the 17 participating countries. The proposed standard is however a useful guide and has much valuable information although the assessment of outside air quantities based on the use of the olf and decipol is the subject of the greatest controversy.

Chemical Sensitivity

Medical historians are able to confirm that hayfever developed in the upper classes and spread slowly down into the other classes through the passage of time, however the reason for this remarkable development has always remained a mystery.

Arguably chemical sensitivity [cell-mediated allergy] fits the aetiology extremely well. Chemical sensitivity appears to have been a major contributing factor in the development of hayfever symptoms amongst the middle and upper classes of society.

 It was very much common place for upper class ladies and gents to wear excessive amounts of strong perfumes and scents which could undoubtedly cause immune system dysfunction in the wearer, and for that matter anyone else who came in close contact with them.

Whilst the rich lived in splendour, the poorer classes were exposed to extreme hardship and many environmental assaults, however, seldom were they exposed to any form of chemical assault (unless due to occupational exposure, e.g. embalming), and it certainly was not common place for the poor to wear perfume.  It would appear that the wearing of perfume may have created a window of opportunity thereby predisposing the upperclasses to hayfever.

Today, anyone who has experienced travelling on public transport, especially first thing in the morning, or worked in an office alongside women, will testify to the overpowering aroma of perfumes in the micro environment. Personal factors like perfumes and aftershaves are recognised by scientists for their importance and contribution to sick building syndrome in the indoor environment.

As far back as the 1930s Rowe had discussed and deliberated about the possibility of chemical allergy. In 1948 Lockey produced several papers about reactions to dyes in medicines and foods. Randolph published examples of many illnesses caused by reactions to chemicals between the late 1950s and early 1960s. In 1962 Carson conclusively demonstrated the devastating effects of chemical agriculture.  Randolph has treated many patients since the 1960s - indicating that exposure to pervasive chemicals in food, water and air is rapidly becoming a major cause of illness.

Scientists and physicians (outside environmental medicine) who study reactions to chemical exposure talk of sensitivity rather than cell-mediated allergy, however to use the term sensitivity is an admission in itself that chemical exposure can cause symptoms. Scientists rarely define sensitivity due to the variable characteristics which may affect  exposure and individual susceptability.

Author - Armitage; copyright 2007

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