Impact of office space ventilation on interior air quality

Outline of reasons and objectives
With service-based employment becoming increasingly proeminent, and nearly 10 million employees working in offices in France, Indoor Air Quality (IAQ) has become an issue for occupational health. However, the nature of the chemical compounds, their concentration, the part played by ventilation and the parts played by the various emission sources remain little known components, and the chronic risk run by the workers is relatively ignored.
It is in this context that INRS initiated a study on IAQ in buildings of the office type. The study aims to deepen the knowledge about the pollution risks to which such employees might be exposed, to study the impact of the ventilation systems, and to propose a diagnostic prevention approach for the employees.

Approach
Fourteen air monitoring campaigns in offices were conducted, thirteen of which in collaboration with the Observatoire de la Qualite de l’Air Interieur. For each campaign, five offices and an outdoor point (more than 70 measurements) were instrumented with a view to qualifying the working environments, as regard both comfort parameters and also exposure to volatile organic compounds (VOCs) and aldehydes present in these environments.
In parallel, an experimental method was developed to assess the impact of ventilation on IAQ in a space of the office type by monitoring the TVOC (total VOC) indicator in real time. For this purpose, a network of metal oxide mini-sensors and an experimental booth reproducing operation of an office were implemented.

Main results
As regards comfort, offices are spaces that tend to be overheated and to have very dry air, as confirmed by the majority of the complaints passed on by the French Prevention Network (Reseau Prevention) on the subject of IAQ. As regards exposure, formaldehyde is a ubiquitous compound present in all of the instrumented office environments; 66% of them had concentrations above the guide value of 10 g/m3 proposed by ANSES (the French Agency for Food, Environmental, and Occupational Health & Safety). Numerous volatile organic compounds, reflecting specific pollution, were also present in these environments. Conversely, exposure to fine particles does not seem to be a major concern in this type of premises.
The original experimental method, developed to understand the impact of ventilation on the IAQ in a space representing an office, made it possible to show the significance of certain little-studied characteristics of ventilation on the distribution of pollutants, in the plane of the respiratory tracts, for the same rate of renewal of the air. It then appeared to be a priority to change the ventilation flow rates to take into account no longer only the occupants as pollution sources (CO2 and humidity), but also the sources of emissions of chemical compounds present in these environments.
Finally, a diagnostic approach was established. This approach proposes, through a set of actions, to predict whether or not a suspected building presents an air quality defect. An INRS guide will make it possible to transfer this approach to the French Prevention Network (Reseau Prevention).

Discussion
The issue of IAQ covers a multitude of aspects that all deserve to be studied in order to estimate, understand, improve, reduce, and prevent exposure of employees in this type of premises.
Two particular aspects are worth discussing: the choice of reference values appropriate to the IAQ issue, and the revision of the ventilation flow rates to take into account the chemical pollution coming from sources other than humans.
A study relating to tertiary premises in which the workers are in contact with new manufactured products is being considered to supplement this work.
An INRS technical day on the issues of IAQ is scheduled in 2017, and publications are being written.