NuAire LabGard NU-540-300E, Operation And Maintenance Manual

Page: 43 / 63

OM0280 Page 43 of 63
Rev 3 July/2021
7.6 HEPA Filter Leak Test
In order to check filter and filter seal integrity, the HEPA filter media and seals must be directly accessible by the measuring
instrument. The challenge material (i.e. PAO) should be supplied in the rear center of the workzone over the intake slots.
The upstream challenge port being common for both filters is located under the work surface with a red cap.
7.6.1 Supply Filter
The diffuser plate, placed below the HEPA to protect the filter during normal usage, may be removed as follows:
The diffuser is secured to the cabinet shell by #1/4-20 acorn nuts located immediately behind the front viewing
window. After removing the fasteners, drop the front of the diffuser plate several inches and pull forward gently.
Note that the diffuser is purposely a tight fit - it is held to the back wall of the cabinet interior by a light push - fit with
projecting studs. To avoid the window high alarm during the filter integrity check, it is desirable to enter the Service
menu and turn on the blower.
Air currents in the room can sometimes contribute to exhaust entrainment on top of the cabinet. This can lead to
false leak readings. In order to reduce the probability of false leak readings, it is recommended to cover half of the
exhaust HEPA filter while scanning the uncovered section of the exhaust HEPA filter.
7.6.2 Exhaust Filter
The exhaust filter is typically more difficult to check since protective grills, charcoal filters, or exhaust transitions
could cover the filter. Access panels are usually provided and should be removed. If an air gap exhaust transition is
provided, the air gap must be sealed with duct tape or other suitable means to prevent contaminated air from
migrating into the exhaust efflux. All exhaust blowers/fans should be turned off during the check.
NOTE: To avoid the window high alarm during the filter integrity check, it is desirable to enter into the
Blower speed adjustment menu and turn the blower on. To accomplish this, perform the
following:
•
Press and hold key,
then press ENT ↑ and ↓ keys sequentially releasing the key after the 3 key sequence.
LED segments will indicate blower speed percentage. However no adjustment is needed, do not adjust!
•
Once filter integrity test is completed,
•
Press key to abort and exit.
Note: If the upstream challenge port is deemed contaminated and not accessible, use both downflow
and exhaust volume for determining challenge concentrations. Use following area information
below with average downflow velocity and spot-check exhaust velocities as measured to
determine volume (CFM) (CMH).
Model
Size
*Supply Area
(ft
2
)(m
2
)
Exhaust Area
(ft
2
)(m
2
)
Model
Size
*Supply Area
(ft
2
)(m
2
)
Exhaust Area
(ft
2
)(m
2
)
300E 6.33 (.588) 1.61 (.150) 500E 10.74 (.998) 4.17 (.387)
400E 8.53 (.792) 3.06 (.284) 600E 12.95 (1.203) 5.00 (.465)
* Measured 4 inches above the bottom edge of the window.
Laskin Nozzle Concentration Formula
# Nozzles x 135 CFM x 100 ug/L Challenge
Downflow (CFM) + Exhaust (CFM) Concentration (ug/L)
# Nozzles x 229 CMH x 100 ug/L Challenge
Downflow (CMH) + Exhaust (CMH) Concentration (ug/L)

=
=
