MERV, ISO 16890 and HEPA Ratings Compared

Oct 11

6 min read

Compliance reviewed by Onur Oncer, SDVOSB Materials compliance lead.

Four incompatible rating systems land in a laboratory air specification. Minimum Efficiency Reporting Value (MERV), the International Organization for Standardization (ISO) 16890 classes, and the high efficiency particulate air (HEPA) grades answer different test questions, and none of them convert into each other. LabTECH Air, part of SDVOSB Materials Technology & Supply LLC, specifies to whichever governs the device.

This shows up on any requirement mixing building ventilation with containment equipment. The air handler serving the room gets one kind of number; the biosafety cabinet inside it gets another. Equipment scope and contracting paths sit in the federal fume hood and air safety procurement guide. This post is about the numbers.

Four Systems, Four Test Questions

ANSI/ASHRAE Standard 52.2, from the American National Standards Institute and the American Society of Heating, Refrigerating and Air-Conditioning Engineers, counts particles before and after a filter and reports removal efficiency by particle size. That produces MERV. ISO 16890 measures something else: how much of an ambient particulate matter fraction the filter removes. IEST-RP-CC001, from the Institute of Environmental Sciences and Technology, sorts HEPA and ultra-low penetration air (ULPA) filters into lettered types. EN 1822, the European Norm, grades that same media at the most penetrating particle size.

Different bodies, different equipment, different challenge aerosols. Treating them as one scale is where specifications go wrong.

What a MERV Number Actually Reports

MERV describes how well a filter captures particles between 0.3 and 10 microns, reported in three size ranges: roughly 0.3 to 1 micron, 1 to 3 microns, and 3 to 10 microns. A filter clears a threshold in the relevant range to earn its step. The published scale runs from 1 to 16. Anything above that is not a MERV number.

The Environmental Protection Agency guidance on MERV ratings carries a caveat worth reading before you write a number into a specification: choose as high a rating as the fan and the filter slot can accommodate. Resistance is the tradeoff. A filter the air handler cannot pull through reduces airflow in a room that needed it.

ISO 16890 Reports a Different Quantity

ISO 16890 groups general ventilation filters by the particulate matter fraction they treat: ePM1, ePM2.5, ePM10, or ISO Coarse for filters reaching no fine-fraction threshold. The vocabulary matches how outdoor air quality is already reported. Federal buyers meet it when the manufacturer is European. It describes a ventilation filter legitimately, and it does not substitute for a MERV number.

HEPA and ULPA Are Graded Somewhere Else Again

Neither MERV nor ISO 16890 reaches this territory. The Department of Energy definition, summarized on the EPA page explaining what a HEPA filter is, sets the bar at removing at least 99.97 percent of particles at 0.3 microns, which EPA describes as the worst case, the most penetrating particle size. Larger and smaller particles are caught more efficiently, so the worst diameter is the one tested.

IEST-RP-CC001 turns that definition into buyable types in North American practice and adds the scan test proving a specific filter, not a filter model, is intact. EN 1822 uses a lettered grade instead: H13 and H14 for HEPA media, U15 through U17 for ULPA, measured at the most penetrating particle size for the medium under test rather than a fixed diameter. ISO 29463 carries the method internationally.

Which Standard Belongs on Which Device

Each line names the device first, then the standard to cite, then the acceptance evidence to ask for.

Building air handler serving a laboratory. ANSI/ASHRAE 52.2 MERV, or ISO 16890 where the manufacturer reports that way. Submittal data plus the test report.
Pre-filter ahead of a terminal filter. MERV. Its job is protecting the expensive filter behind it, not containment.
Biosafety cabinet. HEPA grade plus field certification of the installed cabinet, never the filter datasheet alone.
Cleanroom ceiling module. HEPA or ULPA grade, with an installed leak scan of every module and its frame.
Portable fentanyl, opioid or filtered fume hood. The grade the manufacturer certifies, plus the field test method. Carbon media for vapor is rated separately.
Containment exhaust from a higher tier room. HEPA grade with in-place testing and a documented change-out procedure.

Why MERV 16 Is Not Almost HEPA

That sentence compares a count to a penetration figure taken under a different challenge. MERV reports whether a filter clears thresholds across size bands. The HEPA definition reports penetration at the hardest diameter, verified on the individual filter by a scan. A filter can top the MERV scale and still fall well short of a HEPA grade.

The practical version: if a room needs HEPA, write HEPA and the field test. If it needs a general ventilation filter, write MERV and the pressure drop the air handler can carry. Both on one device produces a requirement nobody can bid.

The Rating Describes the Filter, Not the Installation

Every one of these numbers is earned in a test rig. What protects people is the installed assembly, and assemblies leak at gaskets, clamps and frames long before the media fails. That is why HEPA and ULPA practice includes an in-place scan instead of accepting the factory certificate. Ask for the field test report, not the datasheet.

The honest limitation: on a site with one cabinet and one filtered hood, a formal filter program costs more attention than it returns. An annual purchase order naming the grade and the test does the job.

Buying Filtered Air Equipment Through SDVOSB Materials

SDVOSB Materials Technology & Supply LLC supplies and certifies this equipment through LabTECH Air, the air safety line under LabTECH Environments. Biosafety cabinets come through the Baker partnership, modular clean rooms and ceiling filtration through NICOS Clean Rooms. Which standard applies gets settled during scoping, because it sets what gets tested at acceptance.

The company is a certified Service-Disabled Veteran-Owned Small Business (SDVOSB) and Historically Underutilized Business Zone (HUBZone) small business. It holds no General Services Administration (GSA) Schedule of its own, so GSA orders run through GSA-registered partner vendors. Cooperative purchasing runs through TIPS, The Interlocal Purchasing System, contract 230701. Classification codes sit on the System for Award Management (SAM.gov) entity record under Unique Entity Identifier (UEI) K39HBMPLN4B3. Credentials are verifiable on the Small Business Administration profile: SBA SDVOSB Certified, SBA HUBZone, Lab & Health Cert, and Small Disadvantaged Business.

Verified laboratory past performance includes the U.S. Army Watervliet Arsenal Laboratory, West Point, Johns Hopkins University and Department of Veterans Affairs facilities. Wider scope sits with the LabTECH Environments laboratory division, and fit-outs are covered in the federal laboratory procurement guide. UEI K39HBMPLN4B3 | Commercial and Government Entity (CAGE) code 7YX60 | Employer Identification Number (EIN) 82-2895228.

Frequently Asked Questions

Can a MERV rating be converted into a HEPA grade?

No. ANSI/ASHRAE 52.2 counts particles across size bands and reports a MERV step. The HEPA definition reports penetration at the most penetrating particle size, verified by scanning the individual filter. Different challenge, different quantity, different acceptance test. Any conversion table is a marketing convenience.

Which rating should a federal laboratory specification cite?

It depends on the device, not the project. Air handlers and pre-filters get MERV under ANSI/ASHRAE 52.2. Cabinets, cleanroom ceiling modules and containment exhaust get a HEPA or ULPA grade plus an in-place test. Naming one standard for a whole project is the error.

What is the difference between HEPA and ULPA?

Both are graded on penetration rather than a size-band count. ULPA sits above HEPA on the EN 1822 scale, U15 through U17 against H13 and H14, and suits semiconductor and comparable ultraclean work. Most federal laboratory work is HEPA territory, and ULPA where HEPA is required buys resistance nobody asked for.

Does a higher MERV always improve air quality in the room?

Only if the system can move air through it. EPA advises choosing as high a rating as the fan and the filter slot accommodate, which acknowledges resistance as a real limit. A high-resistance filter in an undersized air handler reduces airflow, and less clean air delivered is the worse outcome.

Does the containment tier change the filter grade?

A Biosafety Level (BSL) tier changes what has to be filtered, sealed and tested around the room more than it changes the media grade on one cabinet. Tier selection drives cabinet class, exhaust arrangement and room verification, covered in what changes between BSL-1, BSL-2 and BSL-3.

Get a Filter Specification Reviewed

Need to source filtered air equipment for a federal, state, or commercial contract? Email LabTECH@SDVOSBmaterials.com, call (917) 216-9400, or start through the contact page. Send the device list and the rooms they serve. If the ducted question is open, the ducted and ductless fume hood comparison settles that first.