A surgical treatment system for contaminated air streams having particulate contamination, polar contamination and/or nonpolar contamination in the gas or vapor stream. A surgical smoke plume treatment system and method provide or define a multi-stage treatment process that mechanically filters the air stream, followed by nonpolar decontamination and then polar decontamination or treatment. The system may be used stand alone or incorporated and used with other surgical instruments or incorporated into an air handler adapted to decontaminate an air stream. A desiccant may optionally be used to remove water from the air stream.

An apparatus for catalytic decomposition of nitrous oxide in a gas stream derived from exhalation air from a patient. The apparatus comprises a casing housing a catalyst bed comprising a catalyst material promoting the decomposition of nitrous oxide. The casing comprises a gas inlet for a first gas stream derived from exhalation air from a patient. The casing comprises a gas outlets. The apparatus comprises one or more tubular members. The casing houses at least a portion of the tubular member. The tubular member comprises a gas inlet for a second gas stream comprising at least a portion of the first gas stream. The tubular member comprises a gas-permeable wall so as to provide one or more third gas streams from the tubular member to the catalyst bed. The third gas stream comprises at least a portion of the second gas stream.

A particulate filter capable of PM capturing performance and pressure drop suppression function. The filter captures a particulate matter PM contained in exhaust gas. The filter includes: a base material including inlet cells each with an opening at an exhaust gas inlet end, outlet cells each with an opening at an exhaust gas outlet end, and porous partitions partitioning the inlet and outlet cells; and an outercoat layer provided on an inlet surface of each of the partitions. The D.sub.90 pore diameter of pores in the outercoat layer is from 1 m to 10 m inclusive. In the outercoat layer, a thickness t1 of pores is from 20 m to 80 m inclusive, and a porosity P.sub.coat of the pores is from 30% to 70% inclusive. According to the outercoat layer with such a configuration, the particulate matter PM can be suitably captured with appropriate control of pressure drop increase.