Ventilation systems often host bacteria and fungi that may be dangerous for the health of exposed people. Essential oils are one means among others to prevent microbial development. Used as a basis for many traditional therapies, these odorant plant extracts have been studied extensively in the medical domain and their effectiveness in the treatment of numerous pathologies has been demonstrated. As opposed to most antimicrobial agents currently used for air disinfection, essential oils are low in toxicity. With a view to proposing an indoor air purification method based on the germicidal and odorant properties of essential oils, we selected a pathogenic test strain and followed the AFNOR NF T72-281 standard. This protocol evaluates on a surfaces level, the disinfection efficacy of volatile antimicrobial agents on airborne contaminations such as bacteria, fungi and spores. The protocol was applied to one of the most active essential oils, mountain savory, and also to a solution of formaldehyde at a concentration of 40% called formol, a chemical reference in hospitals. We demonstrated that the gaseous phase of the essential oil of savory has a lethal effect on Staphylococcus aureus and it has a satisfying bacteria reduction rate close to the total disinfection achieved with evaporated formol.