After introductory considerations on ventilation needs, this memorandum contains a critical evaluation of existing ventilation systems. Single or double flow mechanical ventilation, ventilation adjustable according to the relative air humidity as well as natural ventilation are described with their respective advantages and drawbacks. Five ways of improving ventilation in the future are discussed: informing users, training fitters, promoting collaboration between constructors, approaching designers and house builders and setting up a structure to have only one man in charge of ventilation on construction sites, quality controls and training methods adapted to the specific jobs involved. The present trend in research towards forced ventilation is also examined. Finally, the memorandum addresses the problem of perturbation sources: tumble dryer, cooker hood and fireplace. Recommendations are made as regards the installation of individual mechanical ventilation systems, the detection of in leakage points, points vulnerable to leaks and the plant maintenance. 18 refs.