A sneeze is a powerful protective mechanism for the human body. This involuntary action expels air forcefully from the lungs through the nose and mouth. Its primary purpose is to clear irritants, such as dust, pollen, or pathogens, from the nasal passages and upper respiratory tract.
The Velocity of a Sneeze
Sneeze speed estimates vary, with popular belief often citing speeds as high as 100 miles per hour (mph). However, recent scientific studies using advanced techniques suggest a lower average velocity. Research employing high-speed cameras and particle image velocimetry has observed maximum sneeze velocities around 10 mph (4.5 meters per second). Other measurements have indicated speeds in the range of 35-40 mph, highlighting the variability depending on measurement methodology and individual factors.
The Mechanics of Expulsion
A sneeze begins when nerve endings in the nasal passages detect an irritant. This sensory information is then transmitted to a specialized “sneeze center” located in the brainstem. The brain’s response initiates a coordinated sequence involving numerous muscles.
To generate force, an individual first takes a deep breath, filling the lungs. Muscles in the chest and diaphragm contract suddenly, building considerable pressure within the respiratory system. Simultaneously, the vocal cords and the back of the tongue close off the passage to the mouth, momentarily trapping the air. This pressure is abruptly released as the vocal cords open, expelling air, mucus, and saliva forcefully through both the nose and mouth.
Factors Influencing Sneeze Speed
Sneeze velocity is not uniform, as several factors can influence its speed. An individual’s physiology plays a role, including lung capacity and respiratory muscle strength. Nasal and buccal passage geometry also affects how quickly air is expelled. For instance, nasal passage obstruction, due to allergies or a cold, can increase sneeze flow velocity.
The nature and intensity of the irritant also contribute to its force. Common triggers include dust, pollen, strong odors, or the presence of viruses and bacteria. An individual’s health status, including respiratory conditions or infections, can further modify sneeze strength and speed.
The Far-Reaching Effects of a Sneeze
A sneeze’s high velocity propels respiratory droplets considerable distances. These microscopic droplets can travel well beyond six feet, with some studies indicating a reach of up to 27 feet. Smaller droplets can remain suspended in the air for several minutes, carried by gas clouds generated during the sneeze, extending their range significantly further than larger particles.
This dispersion has direct implications for the spread of airborne particles, including germs and allergens. Viruses, such as those causing influenza or COVID-19, and bacteria can be effectively transmitted through sneeze-generated aerosols. Consequently, practicing good hygiene, such as covering sneezes with a tissue or into the elbow, and promptly washing hands, is important to reduce particle transmission.