To enhance sterilization effect in an equalizing grid while facilitating mounting/demounting thereof by forming the equalizing grid of an alternate laminate of a planar polypropylene sheet and a corrugated sheet and holding the equalizing grid at the air outlet of a refrigeration showcase through resiliency of both sheets.

An equalizer 6 is formed by laminating a planar sheet 6a of polypropylene film and a corrugated sheet 6b alternately while defining a chill vent between them. The root 6b of an upper corrugated sheet 6b is arranged between the crests 6d of a lower corrugated sheet 6b. When a compression force is applied to the equalizer 6, the planar sheet 6a flexes to shrink the equalizer 6. When the equalizer 6 is cleaned, a protrusion arranged on a reinforcing plate 12 is picked and the equalizer 6 is pulled while being shrunk to disengage a protrusion 15 arranged at an air outlet 5 from an engaging hole made in the reinforcing plate 12 thus removing the equalizer 6 easily from the air outlet 5.