The baffles are removably secured in position by a detent mounting system (FIG. 5) including spaced apart tabs 200 which are secured to the shell 42. Each tab is tapped to threadably receive a tubular fitting 203 which internally houses a detent plunger 202 biased by a spring 201. Once the baffle is inserted between a pair of tabs 200, plunger 202 will yieldably engage a generally con cave depression 204 defined on opposite sides of each baffle. Once the baffles 140 are inserted in proper operative position within spaced apart guide slots 208, they will by yieldably maintained in proper operative position upon the engagement of plunger 202 in depression
204. Each baffle may be quickly manipulated via integral handle portions 205 thereof.