Abstract: The disclosure describes a chamber for use in immunizing chickens or the like fowls by treating them with a vaccine which is sprayed in the chamber. Inside an enclosure where the chickens are loaded, there is created a continuous flow of air into which is sprayed a vaccine. A deflector cone is used to make sure that the vaccine-loaded flow of air circulates uniformly throughout the enclosure. Furthermore, the pressure inside the enclosure is maintained negative, i.e. it is at a lower level than the outside atmosphere, to make sure that viral particles do not leak outside the vaccination chamber. Finally, means are provided for flushing the chamber and a system such as a filter or/and an incinerator or the like is used to prevent the escape of viral particles to the outside atmosphere. Vaccination with this chamber is safe, economical and does not pollute the environment.