Abstract: Apparatus and method for an airborne particulate booth, such as a dust or paint, include a velocity sensing device for detecting the velocity of the air flow in the booth, utilizing, in a preferred form, a pendulum mounted sail. The air flow from the booth moves the sail; the sail moves the pendulum; and the pendulum's motion is detected and used to control the booth's air flow intake and exhaust fans or blowers to maintain the air flow at essentially a preset or desired constant velocity. Additionally, the apparatus and method when used in a powder paint booth with powder filters, includes progressive pulsing means which pulse the powder filters in a manner such that the interval between pulses may be automatically and progressively changed to keep the powder filters operating at or near peak efficiency from the time they are installed until the time they can no longer be kept functioning efficiently by pulsing, but must be replaced.