Aerosol therapy is an efficient, but complex procedure. National and international practice guidelines are regularly updated. However, only a few studies have assessed the application of guidelines by users. The aim of this study is to assess the knowledge and practices of physicians and nurses regarding these guidelines.Two self-administered questionnaires were designed by a working team and presented to physicians and nurses of four university hospitals in Paris. A pharmacy resident collected and analyzed the data with the aid of an online survey website.A total of 481 physicians and nurses completed the questionnaires (33 % of physicians and 67 % of nurses). Only 241/480 physicians and nurses (50 %) knew that several intravenous drugs cannot be nebulized. Ninety-four of 422 (22 %) of them always choose oxygen as the driving gas and 239/311 nurses (77 %) think that single use nebulizers can be re-used for the same patient.This survey shows that many physicians and nurses lack knowledge and use inappropriate practices. Based on these results, a booklet has been designed by the working team. This booklet should help health professionals to harmonize practices across hospitals and to follow the guidelines correctly.