ASHRAE Research Project 1480 Report - Food Service Technology ...

Makeup Air Specifications
Displacement Diffusers
To maintain a neutral pressure of zero between the inside and outside of the laboratory,
replacement air was supplied through fourteen floor-mounted displacement diffusers to either
supplement the difference between the local makeup air and exhaust rate or entirely supply the
laboratory when local makeup air was not in operation. These diffusers were located as far away
as possible from the hood, with seven in the front system and seven in the rear system. The
diffusers were balanced left-to-right across each system and each system was then balanced to
ensure similar airflow from each side of the laboratory. The intention was to emulate transfer air
from adjoining spaces and provide a low-velocity air supply, which has been proven to minimize
the influence of replacement air on hood performance. The front system is shown in Figure 16.
Figure 16. Floor Mounted Displacement Diffusers as Used to Supply Makeup Air
2-15
RP-1480