1. Home
  2. Modular Cleanrooms
  3. Fan Filter Units (FFUs), Lights, Ionizers
  4. Explosion-Proof RSR FFU

Explosion-Proof Room Side-Replaceable Fan-Filter Unit
For Class I or II, Division 1 Hazardous Locations

Explosion proof fan filter

Models below are UL and UL-Canadian listed. 
cULus logo
Terra's Explosion-Proof WhisperFlow™ Room Side Replaceable (RSR) Fan-Filter Units allow filter changes without having to breach the Class I or Class II, Division 1 cleanroom barrier. As determined by the National Electrical Code (NEC), these FFUs are safe for continuous use in designated cleanrooms. Filled rigid conduit and wiring installation are included.

The RSR module design means that you save time and money by changing filters inside the cleanroom. The gel-filled channels maintain a tight seal against the explosion-proof cast-iron blower housing so that the clean enclosure isn't compromised, and inconvenient roof access is not necessary.

  • Comply with NEC regulations for Class I/II, Division 1 hazardous locations
  • Average air flow: 650+ CFM (1095 m3/hr) under filter load (2' x 4' 610 mm x 1219 mm, model; see chart below)
  • Uniform, laminar-flow filtered air streams at an average speed of 90 ft/min (0.458 m/sec)
  • Motor is ¼-horse power, direct-drive, fan-cooled and non-sparking for safe operation
  • Select 99.99% efficient HEPA filter (99.99% efficient @ 0.3 µm particles) or ULPA filter (99.999% efficient @ 0.12 µm particles)
  • Reduce downtime for maintenance, and avoid having to recertify the controlled space
  • Installation of wiring and modifications to Power Distribution Module and control panel switches are included
Filter replacement is fast with the easy-open, rotating clamps. Simply turn them to release the filter screen and then lower the gel-sealed filter down from the fan module in the ceiling. Lift the new filter into place and secure the clamps.

  FEATURES & BENEFITS | Explosion-Proof Fan/Filter Units
Alt Text
Pre-Filter Grounding Clip
A grounding wire connects the body of the FFU to a metal wireframe embedded in the pre-filter.
Non-Sparking, Direct-Drive Motor
Explosion-proof motors use a non-sparking polypropylene fan and cast-iron brackets attached to the heavy duty rolled steel frame.
Filter Screen Grounding Clip
Another grounding wire clips to the mesh screen that protects the face of the HEPA filter.

Explosion-Proof Outlet Box
The reinforced outlet box is built to withstand and contain an explosive reaction within the conduit system.

Sealed Wiring Conduit
All FFU wiring is sealed within steel conduit that is joined together by UL-listed explosion-proof fittings.

Roomside Replaceable FFU Roomside Replaceable FFU
Gel channel that seals against "knife" edge on explosion-proof fan housing. Grounded rotating clamps turn to release the filter screen and access the HEPA or ULPA filter.
Filter shipped uninstalled to prevent shifting in the mounting gel that could cause leaks. Also available: Explosion-Proof, non-Room-Side Replaceable fan/filter units.
Explosion-Proof RSR WhisperFlow Fan/Filter Unit: Airflow and Electrical Specifications (120V)
Model Nominal Dimensions*
Inches (mm)

Avg. CFM (m3/h) Airflow ft/min (m/s) Run Amps (Watts) @ 60Hz
2 x 4 23.72 x 47.63 x 19.86 (603 x 1210 x 504) 717 (1218) 102
2 x 3 23.72 x 35.63 x 19.86 (603 x 905 x 504) 602 (1023) 116
2 x 2 23.72 x 23.63 x 19.86 (603 x 600 x 504) 558 (948) 166
* With pre-filter installed
Explosion-Proof WhisperFlow RSR Fan/Filter Unit: Ordering Information
Nominal Dimensions*
Inches (mm)
Power Weight
lbs. (kg)
With HEPA Filter With ULPA Filter
Cat. # Price Cat. # Price
23.72 x 47.63 x 19.86
(603 x 1210 x 504)
120/220 VAC, 60 Hz 116 (53) 6601-24-HRE $ 3,045 6601-24A-URE $ 3,266
23.72 x 35.63 x 19.86
(603 x 905 x 504)
120/220 VAC, 60 Hz 107 (49) -- -- 6601-23A-URE $ 3,266
23.72 x 23.63 x 19.86
(603 x 600 x 504)
120/220 VAC, 60 Hz 100 (45) -- -- 6601-22A-URE $ 3,266
  NEC Type: Explosion-proof, Class I Group C&D, Class II Group F&G, Division 1, Fan-cooled
  Electrical Type: Capacitor start, induction run, single-speed
  Design: 0.25 HP, 1140 RPM, Direct-drive
  Frame Construction: Cast Iron
Filter: 99.99% efficient @ 0.3 µm particles (HEPA); 99.999% efficient @ 0.12 µm particles (ULPA)
Housing: 304 Stainless Steel
Impeller: Forward-curved, non-sparking centrifugal type; factory balanced
Terra Universal Class I/Class II, Division 1 Enclosures
To ensure safe operation, specify a Terra explosion-proof enclosure for operations that entail the presence of combustiblefumes, vapors or dust, such as explosion-proof modular cleanrooms, laminar-flow workstations, or laminar-flow hoods.

FFU Challenge Port

Air filters keep your environment clean, but validating their integrity can be cumbersome and knowing when to replace them is a challenge. Room designs, applications and staffing make each cleanroom unique. Therefore, it’s important to get baseline measurements of your equipment when first installed, and then set up a schedule for regular monitoring.

Tubing fits into both the orange challenge port valve and the Magnehelic® gauge to easily record FFU pressure differential.
Upgrade your fan/filter unit (FFU) to include a Terra-installed Challenge Port that both simplifies leak testing and helps establish a filter replacement schedule. The port is 3/8"-diameter, nickel-plated brass adapter fitting with a white polypropylene plug.

Learn more about Terra's FFU Challenge Port.

Price includes installation on specified FFUs.

FFU Challenge Port
Cat. # Price
6601-99 $ 67

File Type File Name Publication Date
Manual (PDF) Explosion-Proof Room-Side Replaceable Fan Filter Unit
Specifications and instructions for Terra's Room-Side Replaceable (RSR) Explosion-Proof Fan/Filter Unit. See step-by-step instructions on how to change the filter from inside the cleanroom enclosure.
Click to leave a message. 24-hour sales and tech phone support, M - F
Call a Terra FFU specialist direct
Hours: 5:30 - 17:30 M-F
(your local time)
Go to...
Go To