Abstract: An air treatment apparatus for conditioning air or providing ventilation of air includes: a casing of an apparatus main body; a first sensor disposed outside the casing and configured to output a signal in conformity with a first communication standard; a conversion unit configured to convert the signal output from the first sensor into a signal conforming to a second communication standard higher in tolerance to noise than the first communication standard and to output the signal thus converted; and a main control unit disposed in the casing and configured to receive the signal output from the conversion unit.

Abstract: Compactness is enhanced while retaining the performance, noise deadening characteristic and engine output. The ratio of the distance, a, from a gas outlet end, p, of an exhaust pipe to an inner wall of a rear partition wall to an inside diameter ∅A of the exhaust pipe is set in a relation of 0.6≦(a/∅A)<1.2, while the ratio of the distance, b, from a gas inlet end, q, of a tail pipe to an inner wall of a front partition wall to an inside diameter ∅B of the tail pipe is set in a relation of 0.4≦(b/∅B)<1.2, to afford a silencer having an optimum combination of engine output characteristic and compactness while retaining a noise deadening effect.