Biosafety Cabinet Airflow Containment Simulator

Cabinet Controls

Blower speed 80%

Sash opening height 20 cm

HEPA filter loading 10%

Live Readouts

Face velocity

0.50 m/s

Downflow velocity

0.30 m/s

NSF/ANSI 49 status

Compliant

Captured

Escaped

Containment rate

—

How it works

A Class II biosafety cabinet protects the operator with an inward "air curtain" through the front sash opening, combined with HEPA-filtered laminar downflow over the work surface — not a sealed enclosure. Face velocity is governed by continuity:

v_face = Q_supply / A_opening,   A_opening = sash_width × sash_height

NSF/ANSI 49 requires v_face ≥ 0.5 m/s (100 fpm), typically 0.45-0.55 m/s.
Below ≈0.4 m/s the inward barrier can't overwhelm outward
turbulent diffusion — aerosols escape through the opening.

Raising the sash enlarges A_opening, which lowers v_face for the same blower output — exactly why operators are trained to keep the sash near its rated line. A loaded HEPA filter raises static back-pressure, so a fixed-speed blower delivers less flow (lower Q) at the same duty cycle, degrading both the inward face velocity and the downward laminar sweep that pulls droplets to the front/rear intake grilles at the work surface.

Blower speed — sets the volumetric supply flow Q driving both curtains.
Sash opening height — sets A_opening; taller opening trades away face velocity.
HEPA filter loading — chokes flow the way a real loading filter does over its service life.
Release aerosol burst — drops droplet nuclei at the work surface; cyan = airborne, green = drawn into a grille (contained), red = crossed the sash plane (breach).

Airborne droplet Captured (grille) Breach (escaped)

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