Bacteria: Single celled microorganisms ranging from harmless and beneficial to intensely virulent and lethal.

Baffle: Plate or vane used to direct or control movement of fluid or air within a confined area.

Bed Depth: The amount of adsorbent, expressed in length units, which is parallel to the flow of the air stream and through which the air stream must pass. Example: A tray type of adsorber may have a bed depth of 1 inch (25.4mm).

B.E.T.: A method developed for measuring the surface area of granular activated carbon. It is named after the developers of the process: Braunauer, Emmett and Teller.

BFE: Bacteria Filter Efficiency.

Blow-Through: An HVAC system with the fan located upstream of coils, air washer and final filters.

Blower: A fan used to move air under pressure.

BRI: Building related illness. Illness whose cause is related to conditions inside a building.

Brownian Movement: The continuous zig-zag motion of particles (aerosols) in suspension. The motion is caused by the impact of the molecules of the fluid (air) upon the particles.

BTU: Amount of energy required to raise the temperature of 1 pound of water 1 degree farenheit. To raise 1 pound of air 1 degree farenheit requires 0.24 BTU.

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