1.
What are the requirements of the Telcordia NEBS standards pertaining to air filters?
- NEBS GR-63-CORE
R4-45 [93] Foamed polymers shall meet the HF-1 requirements of ANSI/UL 94-1996.
NOTE: Foamed polymer air filter assemblies must also meet the firespread requirements of Section 4.5, “Airborne Contaminants.”
R4-87 [138] All fan-cooled equipment shall be equipped with filters. Fan filters shall be replaceable with equipment operating. Fans used to cool the outside of sealed equipment cabinets need not be fitted with particulate filters.
R4-88 [139] All equipment fan filters used in equipment occupying over 2U of vertical rack space (90 mm or 3.5 in) shall have either a:
| Minimum dust arrestance of 80%, per ASHRAE Standard 52.1, Gravimetric and Dust-Spot Procedures for Testing Air Cleaning Devices Used in General Ventilation for Removing Particulate Matter, 1992, or |
Minimum Efficiency Rating Value (MERV) of 4, per ASHRAE Standard 52.2, Method of Testing General Ventilation Air Cleaning Devices for Removal Efficiency by Particle Size, 1999. |
R4-89 [176] All equipment fan filters used in equipment occupying 2U of vertical rack space (90 mm or 3.5 in) or less shall have either a:
| Minimum dust arrestance of 65%, per ASHRAE Standard 52.1, Gravimetric and Dust-Spot Procedures for Testing Air Cleaning Devices Used in General Ventilation for Removing Particulate Matter, 1992, or |
Minimum Efficiency Rating Value (MERV) of 2, per ASHRAE Standard 52.2, Method of Testing General Ventilation Air Cleaning Devices for Removal Efficiency by Particle Size, 1999. |
R4-90 [140] Fan filters shall have a minimum fire rating of Class 2 per UL 900, Standard Air Filter Units, 1994.
NOTE: Polymer filter media must also meet the fire-resistance requirements per Section 4.2.3.1, “Material/Components Fire-Resistance Criteria.”
R4-91 [141] Construction and system fit of equipment fan filters shall prevent any air bypass. Inadvertent leakage that may result from mechanical fits or tolerances, (examples may include spaces between circuit pack face plates, connector or cable matrices, chassis screw or mounting holes, etc.), is not considered bypass.
R4-92 [142] Equipment shall have provision for fan-filter replacement with the fans shut down or blocked to prevent handling contamination. Some designs where the filters are withdrawn from the air flow for removal (e.g., door mounted filters) satisfy the intent of this requirement.
R4-93 [143] The equipment manufacturer shall provide a method for determining equipment fan filter replacement schedules.
O4-94 [144] If possible, active alarming should be provided to indicate the need for fan filter replacement.
O4-95 [145] It is an objective that equipment fan filters are disposable and not the types that require removal and cleaning.
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NEBS GR-78-CORE
R8-3 [670] All fan-cooled equipment shall be configured with filters.
R8-4 [671] All equipment fan filters shall have a minimum dust arrestance of 80%. This represents a low efficiency 10 to 15% American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE) dust spot rating.
R8-5 [672] Fan filters shall have a minimum fire rating of Underwriters Laboratories (UL) Class 2.
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2. Are Universal Air Filter products RoHS Compliant?
All Universal Air Filter products -- Quadrafoam, Unifoam, Polyester, Windowpane, Flexframe, and Dual EMI -- are RoHS Compliant with the EU Directives for banned substances. Whether a framed air filter assembly, or media only pad, all air filter products are RoHS Compliant. Framed filter assemblies containing special metal finishes are treated with a RoHS Compliant or chrome-free, chemical conversion coating. All Telcordia NEBS, UL 94 HF-1 flame resistant media for telecom and datacom applications are RoHS Compliant. Medical air filters, military communications air filters, and power-gen air filters are also RoHS Compliant. Click here to view our RoHS compliance document.
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3. What is the recommended method of cleaning Universal air filters?
Four easy ways to clean Universal's Windowpane, Quadrafoam and Uni-Foam Air Filters:
- Vacuum Clean - A few passes of a vacuum cleaner will remove accumulated dust and dirt in seconds.
- Blow with Compressed Air - Point compressed air nozzle in opposite direction of operating air flow (blow from exhaust side toward intake side).
- Cold Water Rinse - Under normal conditions the foam media used in Universal's WINDOWPANE, QUADRAFOAM and UNI-FOAM filters require no oily adhesives. Collected dirt is washed away quickly and easily using just a standard hose nozzle with plain water.
- Immersion in Warm, Soapy Water - Where stubborn air-borne dirt is present, the filter may be dipped in a solution of warm water and mild detergent. Then simply rinse in clear water, let stand until completely dry and free of moisture, and return to service.
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4. What features in addition to air filtration can I receive if I specify Universal?
- Air-Diffusion - Proper thermal management should also consider air-straightening capabilities of the air filter to ensure sufficient cooling. Many ventilation systems generate turbulent flow at the inlet when air rapidly enters the enclosure while being sliced by fan blades, then is forced to turn sharp corners. This turbulence creates noise, slows the airflow before exiting, and reduces the effective cooling. Hence, the goal for the OEM designer is to select an air filter that both captures particulates and produces adequate laminar airflow.
Distribution of laminar airflow is critical. Laminar airflow insures that each card receives the same amount of air at the proper velocity. Otherwise, components may fail prematurely due to heat build-up. Designers previously had to use expensive perforated metal or aluminum honeycomb to get the air in the right place. Universal Air Filter Company can readily eliminate the need for a separate, expensive air-straightener.
Air straightening decreases the vortices and input power, increases downstream velocity, and maintains velocity over greater distances. This prevents large vortices from forming and distributes the pressure drop more uniformly across the chassis. The air filter media itself plays a major role in keeping airflow laminar.
- EMI Shielding - Potentially disruptive EMI/RFI noise can be a problem with enclosures where forced air cooling is used in the equipment's thermal management plan. To protect against EMI/RFI noise, honeycomb or perforated metal panels were commonly specified separately and permanently mounted to shield moderate levels of EMI emissions. Universal provides air filtration and EMI shielding in a single, low-cost assembly that is compact and removable. The Dual EMI Honeycomb air filter integrates the honeycomb EMI shield into the air filter assembly. The honeycomb structure consists of "cells" that are engineered to trap and absorb EMI noise while maintaining 95% to 99% openness for minimal airflow impedance.
Because Dual EMI Honeycomb air filters are removable, the air filter and shield are easily cleaned and reinstalled in the device as required. Dual EMI Honeycomb air filters meet the stringent filtration performance and flammability requirements of CE and UL. They deliver more than 60dB attenuation over a frequency range of 10 kHz to 1 GHz. A gasket installed around the frame assures conductivity of the frame to the enclosure, and the honeycomb structure reflects and absorbs EMI.
- Full Compliance with Industry Standards & Classifications - Universal Air Filter Company is capable of meeting primary standards and classifications that OEM designers should look for when specifying air filters. Universal products are:
- Telcordia NEBS certified
- UL 94 recognized
- UL Class 2 classified
- CE certified
We also help designers meet the stringent requirements of UL 60950 (formerly UL 1950), ETSI, and EN 60950 for Europe. By specifying Universal, OEM designers can be assured that the air filter has been independently laboratory tested in accordance with MIL-STD-285 for EMI shielding and ASHRAE 52.1-1992 for particulate arrestance.
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