Retrotec USACE - Manual (Page 269)

Appendix D D139
D.7.10.11 Supply Air Jet Disturbs Air Flow around the Hood and
Results in Heat, Grease, and Smoke/Vapor Spillage (Ineffi ciency)
Figure D228. Air jets are supplied toward the hood (top left), reconfi gure four-way makeup air
diffuser (top right), low-velocity air diffusers (bottom left) “push” the convective plume into the
hood (bottom right).
Local four-way makeup air diffusers force air down the exhaust hood face and
draw appliance effl uent plumes (heat, grease, and smoke/water vapor) out
into the kitchen space, increasing air conditioning requirements. Converting
these diffusers to two-way diffusers that direct air parallel to the hood’s face or
low-velocity thermal displacement air distribution units can dramatically im-
prove the hood’s ability to capture and contain the appliances’ effl uent plumes
(Figure D228). Low-velocity air diffusers using the natural buoyancy of the
supply air help “push” the convective plume into the hood. This allows for 15%
reduction of hood exhaust air fl ow.