(JAPAN) — Face shields aren’t as impenetrable as the spangly one Captain America wields on his arm — that’s the word from researchers at Fukuoka University in Japan.

The scientists say the plastic guards are, in fact, no match for the biological function for which most wear them: a sneeze.

The researchers modeled the physics of a sneeze, and discovered the microscopic particles can travel around the edges of a face shield, and onto your face.

Behind the findings are complex physics of fluid dynamics and “high velocity airflow in conjunction with vortex rings.”

Essentially, a sneeze fires air through someone’s pie hole at high speed, and in the shape of a donut — think of a smoke ring — and that ring shape, combined with the velocity, can easily squeeze around and over the shield, spreading respiratory particles onto the wearer.

The experts agreed that face shields do offer some protection from COVID-19 and other respiratory ailments, but only when used in conjunction with a face mask. 

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