Background The bacterial genera Streptococcus is often studied within the context of its more pathogenic members. However, the abundance of Streptococci within respiratory fluids, and general absence from the environment means that it serves as an ideal marker for airborne respiratory particles, and therefore airborne transmission risk. Methods Strep selective agar was placed into an Andersen Impactor, allowing for air to be sampled onto the plates, and the colonies counted to quantify the sampled Streptococci. The generation of Streptococci by vocalisation, both directly from healthy volunteers and within controlled ‘meetings’ was measured. Results Streptococci were generated by vocalisation at an average rate of 7 CFU per minute. Two peaks in the particle size transporting the bacteria were observed, one in the first and one split between the fourth and fifth stages of the impactor, corresponding to particles >7 µm and particles 1-3 µm in diameter. Varying the type of vocal activity identified the larger particles as originating from the oral cavity and the smaller particles from the larynx. Within the controlled meetings, Streptococcus was readily detected within the meeting room air, with increased vocalisation increasing the sampled CFU. The Strep selective agar appeared specific to organisms originating within the respiratory tract, with no colonies growing on the agar when it was exposed to skin, dust, or air sampled from unoccupied spaces.       Conclusion Quantification of airborne Streptococci provides a simple, broadly applicable tool by which numerous aerobiological research questions regarding the factors influencing airborne infection risk can be explored.