After a review of CFD models and a simplified (zonal) models predictions, a simplified procedure, based on charts and non dimensional groups, is proposed in order to evaluate the ventilation rate through an open vertical window.

The author gives practical advices in the design of local exhaust ventilation system (mainly hoods) to capture the contaminant and general ventilation systems to dilute the offending chemical contaminant to acceptable effects. The effect on local environment is studied too.

The National Institute of Health has conducted an extensive study on the issue of operating room ventilation system and its effect on protection of the chirurgical site. A CFD code using a finite-volume code was validated with experimental data.

Air networks are very important in indoor air quality of the patient environment. Qualitative and quantitative criteria for the design, installation and maintenance of the air network must be defined in the project.

For hospitals, air filtration is obviously a very important point in the control of nosocomial infections. A strategy and reference points are presented .

In hospitals, legionella, humidification and indoor air quality can be mastered with simple technical equipment.

Comments about the project of the new french standard NF S 90-351 "Clean rooms and related controlled environments in medical establishments" and the consequences on the design approach of clean rooms to master airborne contamination are given.

The french standard NF S 90-351 has been modified to include a wider field of application. This standard now takes into account previsional aspects. It is needed to define "areas at risk", and materials and equipment performances.

Air tighness of ventilation network is very important, so the manufacturers have developped sets of new sealed fittings. These new equipments have been tested in CETIAT laboratory. Results show good performance in term of air tighness and installation time.

Results of on site measurements in office buildings relative to the performance characteristics of five ventilation networks are presented. The poor air tightness is responsible for defects and bad performance.