Essential oils have a sedative effect on stress, and are also known to have antibiotic and anti-carcinogenic effects. These compounds have long been used as natural microbial agents, and have recently been added to a number of pharmaceutical, food and cosmetic products. Controlling the exposure to allergens and pathogens are important factors for the treatment of allergy, and potentially reducing the risk of sensitization and infection. Low humidity, at levels under 35%, may affect human comfort and health during the winter. Patients and other individuals require optimal humidification to maintain a moisturized respiratory tract necessary for protecting against bacterial infection. We designed an analytical system to examine the effects of aromatherapeutic essential oils on airborne bacteria. The antibacterial activities of essential oils were assayed using agar plate air-sampling methods. A bacterial suspension was sprayed into a bio-clean room through the upper holes using a spray gun. Free-floating airborne bacteria were collected from the bio-clean room (blank) in blood agar plates for 10 sec using an air sampler. Three different concentrations of essential oils (0.0005, 0.005 and 0.05 ppm) were then sprayed into the bio-clean room for 5 min. Free-floating airborne bacteria were collected every 10 min for 10 sec each. Treatment with 0.0005 ppm essential oils inhibited the growth of colonies; this effect appeared to persist after 60 min. Decreased bacterial colony growth was more apparent in the presence of 0.005 ppm and 0.05 ppm essential oils than 0.0005 ppm. These effects were observed after 60 min compared to the control (distilled water). These results indicate that essential oils are able to inhibit the growth of airborne bacteria.