No respiratory protection guide specific to biological hazards exists. To make up for this deficiency, the review committee for Schedule 1 of the Regulation respecting occupational health and safety asked the IRSST to produce such a document. The authors will take into account two types of hazards: infections associated with living bioaerosols, and the immunological or toxic reactions caused by microorganisms, even dead ones. The guide that will result from their work will be useful to workers exposed to biological hazards and to the people responsible for protecting them by determining the need to wear respiratory protective equipment and by making it easier to choose the most appropriate device, based on the case.