53 to raise the baffle and create an opening 57 for air flow to pass through the position of the baffle is preferably adjusted at an angle from the horizontal between a closed position 0 u00b0 or an open position where 30 u00b0 the angle of the baffle 44 and size of the opening 57 is adjusted as desired to control the air flow amount and direction to meet intended purposes preferably the baffles are adjusted to an angle of between 5 u00b0 and 15 u00b0 from the horizontal the baffles 44 may optionally be connected to locking means 59 for locking the baffle at the desired raised angle choosing a suitable type of locking means employed is within the skill of one in the art stationary baffle means 51 may extend substantially horizontally from the cross member 25 to the downstream wall not shown see 45 of fig3 generally 10 to 40 of the distributor cross section may be baffled preferably 20 to 30 pressure gradients as measured between outer walls 41 and 45 range from a lower limit of 0 5 inches of water up to a maximum of 1 5 inches water the normal operating range being 1 0 inches water the induced incremental horizontal velocity component can be from 0 fpm up to 300 fpm with the optimum incremental increase being something less than 200 fpm fig5 illustrates graphically by curve 1 and 2 the comparative advantages that accrued in tests of the baffled and conventional units the distributor had six rows of impellers while the suction box was off set by about one row.