An air purifier includes a lower housing, a surface thereof is provided with air inlets, and an upper part thereof extends inwards to form an annular first guide wall; a bracket, an inner surface of the filter element, and a bottom wall of the lower housing together enclose an air inlet channel; an upper housing, installed on the lower housing, and a top of the upper housing is provided with air outlets; a wind wheel, rotatably arranged inside the upper housing and coaxially arranged with the air inlet channel; the upper housing, the first guide wall, and the bracket together enclose an air outlet channel; the air enters the lower housing from the air inlets and is filtrated by the filter element, then enters the air inlet channel, then enters into the air outlet channel through the communication holes, and expels out of the air outlets.

A wet scrubber can be used to capture dust particulates from a bulk powder conveyed into a mixing system. The mixing system can be used to form a treatment fluid for use in an oil and gas operation, such as a cement slurry. The wet scrubber includes a first section having two sets of baffles that create a first and second stage. Air and the dust particulates flow into and through the baffles of the first stage and turbulently mixed with water in the wet scrubber to capture the dust particulates. The air and any remaining dust particulates then flow into and through the baffles of the second stage and turbulently mixed with the water. One or two additional sections, each having baffles, can be included to accommodate varying air flows into the scrubber. The baffles in the various sections can be lower in the water than other sections.