The human sneeze, a common and often underestimated bodily function, involves a surprising amount of force and speed. This involuntary expulsion of air is a complex physiological event designed to clear irritants from the nasal passages. Exploring the mechanics behind a sneeze reveals a fascinating interplay of biological systems and physical forces.
The Speed of a Sneeze
The speed at which a sneeze expels air and particles can vary, and historical estimates have sometimes been significantly higher than recent scientific measurements. Earlier beliefs suggested speeds around 100 miles per hour (mph) or even up to 224 mph, but these figures often stemmed from indirect calculations rather than direct observation. More recent studies, utilizing advanced imaging techniques, provide a different perspective. For instance, some research indicates that the maximum velocity of the expelled air is around 10 mph (4.5 meters per second).
However, the speed of individual particles or mucus ligaments within a sneeze can reach higher velocities. Some experiments have shown individual particles moving at approximately 30 mph (14 meters per second), while strands of mucus, referred to as “ligaments,” can achieve speeds of up to 80 mph (35 meters per second). These variations depend on factors such as individual physiology, the type of irritant, and how the sneeze is expelled.
The Biology of a Sneeze
A sneeze, medically known as sternutation, is a reflex action triggered when irritants stimulate the nasal lining. This stimulation sends signals through the trigeminal nerve to the brain’s sneeze center. The brain then orchestrates a coordinated muscular response involving several parts of the body.
Initially, a deep breath is taken, filling the lungs with air. The epiglottis, a flap of cartilage, closes, and the vocal cords tighten, trapping the air within the lungs. Simultaneously, muscles in the chest, throat, and abdomen contract forcefully, building significant pressure within the respiratory system. This pressure is then suddenly released as the epiglottis and vocal cords open, expelling air, mucus, and saliva through the nose and mouth.
How Far Sneeze Particles Travel
The force and speed generated during a sneeze enable expelled particles to travel considerable distances. The travel distance of droplets and aerosols is influenced by their size and environmental conditions. Larger droplets tend to settle quickly, often within a few feet of the sneezer.
However, smaller particles and aerosols can remain airborne for longer periods. Researchers have found that these smaller particles can be encased within a “multiphase turbulent buoyant bubble,” a gas cloud that extends their travel range significantly. This phenomenon allows some particles to travel much farther than previously thought, potentially up to 27 feet or even 200 feet for the smallest particles. Air currents and the environment also play a role in how widely these particles disperse.
Public Health Implications of Sneeze Force
The considerable force and distance of particle travel during a sneeze have important public health implications. They serve as a primary way for airborne pathogens, such as viruses and bacteria, to spread. The expelled droplets can contain infectious agents that are then inhaled by others or settle on surfaces.
Understanding how far sneeze particles can travel underscores the importance of measures to reduce transmission. Covering the mouth and nose with a tissue or the crook of the arm helps to contain the expelled particles, limiting their spread into the surrounding environment. This simple action can reduce the dispersal of potentially infectious droplets, contributing to the prevention of illness transmission.