A sneeze is an involuntary expulsion of air and particles from the nose and mouth. This rapid reflex serves as a protective mechanism, primarily aimed at clearing irritants from the nasal passages. It removes foreign matter like dust, pollen, smoke, or pathogens that may have entered the respiratory system.
Measuring Sneeze Velocity
Determining the exact speed of a sneeze has been a subject of scientific inquiry, with various studies yielding different results based on their methodologies. An older, widely cited estimate suggested sneeze velocity could reach 100 meters per second (224 miles per hour). This estimate came from mid-20th-century inferences by William Firth Wells, who estimated air speed based on airborne droplet formation rather than direct measurement. More recent observations, however, present significantly lower speeds.
A 2013 study, for instance, used high-speed cameras to track sneeze plumes, finding a maximum velocity of approximately 4.5 meters per second (10 miles per hour). This research focused on the speed of the expelled air plume itself. Other investigations, like those by Lydia Bourouiba at MIT, used advanced high-speed cameras to analyze sneeze dynamics. Her findings indicated that the air from a sneeze can travel at average speeds ranging from 110 to 160 kilometers per hour (68 to 99 miles per hour). Individual particles within the sneeze could reach speeds of 14 meters per second (30 mph), with mucus strings potentially moving up to 35 meters per second (80 mph). The variation in reported speeds often stems from whether researchers measure the velocity of the air plume, specific particles, or mucus, as well as differences in individual physiology and measurement techniques.
The Mechanics of a Sneeze
The forceful expulsion of a sneeze results from a precise physiological sequence initiated by irritation in the nasal passages. Specialized nerve cells in the nose detect foreign particles, sending a signal to the brain’s sneeze center in the brainstem. This signal triggers a coordinated response involving multiple muscle groups throughout the body.
The brain sends signals to the muscles of the face, throat, diaphragm, and chest, including the intercostal and abdominal muscles. A deep breath is taken, and these muscles rapidly tense. Pressure builds within the lungs as the vocal cords close and the chest muscles tighten, with the diaphragm pushing air forcefully upward. The soft palate and uvula depress to partially close the passage to the mouth. This action accelerates the air ejected from the lungs primarily through the nose, resulting in the sudden, powerful burst of air and particles that defines a sneeze.
Why Sneeze Speed Matters
The high velocity of a sneeze has significant implications for public health and hygiene. This powerful expulsion allows for the wide dispersal of respiratory droplets into the surrounding environment. A single sneeze can release tens of thousands of tiny droplets, consisting of mucus, saliva, and potentially disease-causing pathogens like viruses and bacteria.
These propelled droplets can travel considerable distances; a fine mist from a sneeze can spread up to 8 meters (26 feet). While larger droplets settle quickly due to gravity, smaller, aerosolized particles can remain suspended in the air longer and travel further, influencing the spread of infectious diseases. This dispersal mechanism highlights the importance of covering one’s mouth and nose when sneezing, typically with an arm or a tissue. This simple action helps contain the expelled droplets, reducing the spread of germs and contributing to better public health outcomes.