Whereas in the cases of 4 and 2 ACH these particles spread along the ceiling before returning to the exhaust grille
To encourage air mixing, the exhaust grille
should be located at a point remote from supply.
At present, patient wards with mixing ventilation usually have an exhaust grille
installed in the lower part of the restroom door, and some air is extracted through the grille to keep the restroom at a lower pressure than that in the wards.
An exhaust grille
, a rectangular opening 0.3 m by 0.6 m, located in the false ceiling in the corridor outside each cubicle and outside the nurses' station, recirculates 70% of the air supply back into the fan-coil unit.
A single exhaust fan is used with an exhaust grille
in each bathroom.
After closing the exhaust grille
doors, you need to secure them in place with the 100-600 lb-ft torque wrench, NSN 512001-113-9564, from your TM's additional authorization list.
With air-scoop gills, wacky hockey-stick tail-lights and a pepperpot rear exhaust grille
, it's butch, brawny and brazen.
Figure 1 (previously published in my February 2014 column "Restroom Exhaust Systems") shows a computational fluid dynamics (CFD) simulation of a typical exhaust grille
. Note the velocity vectors are only high right near the grille; more than 2 ft (0.6 m) or so away from the grille face, the velocity vectors are close to zero.
Also, fumes from the engine compartment that would normally be vented through the exhaust grille
are forced into the driver and crew compartments.
This study demonstrates that the supply airflow paths, induced airflow paths, and exhaust grille
placement can work collaboratively to establish protective and effective contaminant control.
In February's Engineering Notebook column on restroom exhaust, I agree with Steve Taylor's approach in making a seemingly simple element such as restroom design better by looking at the exhaust rate, the exhaust grille
quantity and the makeup air design.