Radon in the Workplace: Testing Requirements for Commercial Buildings

Radon exposure in workplaces is a hidden health risk, and the rules covering it are not what most commercial building owners assume. There are two different numbers in play, set by two different agencies, and they are 25 times apart. Which one applies to your building decides whether you have a compliance problem, a health problem, or both.

Is radon testing required in commercial buildings?

No federal law requires you to test a commercial building for radon, but if you do test and the result is high enough, OSHA’s ionizing radiation standard does apply to you.

The requirement sits in three separate places, and they do not agree with each other:

• OSHA, 29 CFR 1910.1096. Issued in 1971, this sets the maximum permissible concentration of radon-222 in the workplace at 100 pCi/L, averaged over 40 hours in any workweek of seven consecutive days. A sign must be posted where levels exceed 7.5 pCi/L. It applies to most workplaces, but not to state and local government, marine terminals, agricultural operations, construction operations, or workplaces outside OSHA jurisdiction.
• EPA, the 4 pCi/L action level. EPA recommends fixing a building at 4 pCi/L or above. That figure was set for homes and schools, it is guidance rather than an occupational standard, and it does not carry the weight of law.
• New York State. There is no statutory requirement to test a home or a commercial building for radon in New York. The only explicit reference is 8 NYCRR 155.5(m), which requires school districts to be aware of the geological potential for high radon and to test and mitigate as appropriate. The Department of Health recommends schools test every five years, or every two with a mitigation system in place, during winter, and remediate at 4 pCi/L or above.

So a commercial building can sit at 40 pCi/L, be ten times the level EPA says to fix, and still be inside the OSHA limit. That is the gap worth understanding before you commission anything.

The 25 times gap between the OSHA limit and the EPA action level

OSHA’s radon limit is 100 pCi/L. EPA’s action level is 4 pCi/L. The OSHA figure is a legally enforceable occupational ceiling written in 1971 and tied to Nuclear Regulatory Commission radiation limits. The EPA figure is a health-based recommendation written for houses.

Most commercial radon content quotes only the 4 pCi/L number, which leaves building owners with two wrong impressions at once: that 4 pCi/L is a legal threshold in a workplace, and that anything under it is a clean result with no further duty attached. Neither is accurate.

Here is what that means in practice. Clearing the OSHA limit is a compliance outcome. It is not a statement that the building is safe for the people who spend forty hours a week in it, because the health evidence behind EPA’s 4 pCi/L has not changed just because a different agency set a different number half a century ago. EPA estimates radon causes about 21,000 lung cancer deaths a year in the United States, and it is the leading cause of lung cancer among people who have never smoked.

The practical consequence for a commercial building owner is that there are two questions, not one, and a result only answers whichever you asked. Am I compliant? is measured against 100 pCi/L and the 7.5 pCi/L posting trigger. Is this building healthy to work in? is measured against 4 pCi/L. Deciding which question you are asking before the samples go out is what stops a report being useless to you later. The same principle applies to any environmental result, and interpreting your environmental testing report covers how to read one properly.

Common sources of radon in commercial buildings

Radon is a naturally occurring radioactive gas formed when uranium in soil, rock and water breaks down. It dissipates harmlessly outdoors. Indoors it accumulates, and in a commercial building the entry routes are structural rather than accidental.

• Cracks and joints in slabs, foundation walls and floor-wall junctions.
• Sumps, floor drains, utility penetrations and elevator pits.
• Below-grade space: basements, underground parking, mechanical rooms and lower floors.
• Crawl spaces with exposed soil.
• Well water used on site, which can release radon when it is agitated.
• Some building materials derived from rock and soil, which contribute a smaller share than soil gas but are an occupational source of radon in their own right.

Ventilation design matters as much as geology. A building with a negative pressure differential at slab level pulls soil gas in, which is why radon in commercial buildings often concentrates in the places staff occupy for whole shifts rather than in the spaces nearest the soil.

How commercial radon testing actually works

Commercial radon testing follows a different protocol from the home test kit most people picture, and the standard that governs it changed recently enough that a lot of published guidance is out of date. Radon testing for commercial buildings differs from a residential test in three ways that matter: the scope is set room by room, the building has to be in a controlled ventilation state, and the report has to document the method it followed.

The current measurement protocol for this building class is ANSI/AARST MA-MFLB-2023, “Protocol for Conducting Measurements of Radon and Radon Decay Products in Multifamily, School, Commercial and Multi-Use Buildings”. It consolidated the two earlier standards, MAMF for multifamily and MALB for schools and large buildings, into one document, and compliance with it took effect on 1 December 2023. If a proposal you are reading cites MAMF or MALB on their own, it is citing a superseded standard.

What that means when you commission workplace radon testing services for a real building:

1. Every occupied ground-contact room gets measured, not a sample of them. Radon varies room to room, so a single reading in a lobby tells you about the lobby. Testing scope is set by which rooms sit on or below grade and which are occupied.
2. Season and building operation are controlled. Levels run higher in winter and under closed-building conditions, which is why the Department of Health recommends winter testing for schools. HVAC has to be running in its normal occupied mode, because testing a building in an unusual ventilation state produces a number that describes nothing.
3. Placement and duration follow the protocol. Devices go in the occupied breathing zone, away from drafts, exterior walls and supply diffusers, for the exposure period the method requires.
4. Elevated results get confirmed before anyone spends money. A single short-term result is a screen. Commercial radon mitigation is a construction project, and it should be commissioned off a confirmed measurement rather than one device.
5. The report states the method, the device, the dates and the conditions. A number with none of that attached cannot be defended to a tenant, an insurer or a buyer.

UNYSE conducts radon sampling as part of environmental sampling during building assessments, renovations and demolitions, alongside PCBs, soil and metals. The same field discipline that governs air monitoring on New York job sites applies here: the conditions under which a sample was taken are part of the result, not a footnote to it.

Mitigating radon in commercial buildings, and why testing brackets the work

Radon mitigation in commercial buildings is engineering work, not a product you install. The common approaches are active soil depressurisation, which uses a fan and a vent stack to draw soil gas out from under the slab before it enters, sealing of entry routes as a supporting measure rather than a standalone fix, and adjustments to the HVAC pressure regime so the building stops drawing gas in.

Scale is what separates this from a house. A large slab may need several suction points, a design that accounts for sub-slab permeability, and a fan sized to the building rather than to a catalogue. That is why workplace radon mitigation is specified by a designer working from measured data.

Testing sits on both ends of that project, and this is the part building owners most often leave out of the budget:

• Before. A confirmed, protocol-compliant measurement establishes which areas are elevated and by how much, which is what a mitigation design is sized from.
• After. A post-mitigation measurement is the only thing that demonstrates the system worked. A fan running is not evidence of a reduced level.
• Ongoing. Mitigation systems degrade, fans fail and buildings get re-partitioned. The Department of Health’s school guidance of retesting every two years with a system in place is a reasonable model for a commercial building too.

UNYSE performs the measurement and the verification, not the mitigation installation. That separation is deliberate: the party confirming a mitigation system worked should not be the party paid to install it.

Industries most at risk of radon exposure

Risk follows building geometry and occupancy hours rather than industry sector, but some workplaces combine both.

• Below-grade retail, restaurant kitchens and back-of-house areas where staff work full shifts underground.
• Parking structures and the offices attached to them.
• Schools, day care and university facilities, which is why these are the occupancies the measurement standard and 8 NYCRR 155.5(m) name explicitly.
• Warehousing, manufacturing and factory occupancies built on slab with limited ventilation.
• Healthcare and institutional buildings with occupied lower levels.
• Water treatment and any operation handling well water.

Radon is one of several hazards that behave this way in commercial property, and the top environmental hazards in commercial buildings covers the others. Where radon is part of a wider air quality question, how air quality affects workplace productivity is the related read.

FAQs about radon in the workplace

What is the OSHA limit for radon in the workplace?

OSHA sets the maximum permissible concentration of radon-222 at 100 pCi/L, averaged over 40 hours in any workweek of seven consecutive days, under 29 CFR 1910.1096. A sign must be posted where levels exceed 7.5 pCi/L.

Why is the EPA action level so much lower than the OSHA limit?

They answer different questions. EPA’s 4 pCi/L is a health-based recommendation developed for homes and schools, reflecting long-term residential exposure. OSHA’s 100 pCi/L is an occupational ceiling written in 1971 and tied to Nuclear Regulatory Commission radiation limits. EPA’s figure is guidance and does not carry the weight of law; OSHA’s is enforceable. A building can clear the OSHA limit and still sit far above the level EPA says to fix.

Is radon testing required in New York commercial buildings?

No. New York has no statutory requirement to test a home or a commercial building for radon. The only explicit reference in state regulation is 8 NYCRR 155.5(m), which requires school districts to be aware of the geological potential for high radon levels and to test and mitigate as appropriate. Bills to mandate school testing have been introduced but are not law. In practice, testing in a commercial building is usually driven by something other than a statute: a real estate transaction, a lender or insurer, a tenant request, an employee concern, or a renovation that changes the building’s pressure regime. If your building has occupied space at or below grade and has never been measured, you do not have a number to make a decision with.

How long does commercial radon testing take?

The exposure period depends on the device and the method used under ANSI/AARST MA-MFLB-2023, and the building has to be in its normal occupied ventilation state throughout. Scope is set by how many occupied ground-contact rooms there are, so a single-storey building on slab and a below-grade parking structure with offices are different jobs.

Can I use a home radon test kit in a commercial building?

A consumer kit will give you a reading, and for your own early information that has some value. It will not produce a result that follows ANSI/AARST MA-MFLB-2023, and it will not carry the method, device, date and building-condition documentation that a tenant, insurer, lender or regulator will ask for. If the number is going to be used by anyone other than you, it needs to come from a protocol-compliant measurement.

What to do next

If your building has occupied space at or below grade, the first step is a protocol-compliant measurement of those areas, not a mitigation quote. Decide before you start whether you are measuring against the OSHA limit, the EPA action level, or both, because that decides the scope and how the result gets reported.

UNYSE has tested New York buildings since 1993 and conducts radon sampling as part of building assessments across the state. Send us the building type, the floors in question and what the result needs to satisfy, and we will tell you what testing it needs. You can also see the full range of on-site environmental services we run.

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About the author

This article was written by Andrew J. McLellan, President and Founder of Environmental Education Associates, UNYSE’s sister company. He has overseen environmental safety training and consulting in New York since 1992, working alongside UNYSE’s team of 20 or more certified professionals. UNYSE Environmental Consultants has tested, guided and cleared New York buildings since 1993. Learn more about the UNYSE team here.

Sources: OSHA 29 CFR 1910.1096 and OSHA standard interpretations on ionizing radiation in the workplace. US EPA radon action level and radon health risk estimates. ANSI/AARST MA-MFLB-2023, Protocol for Conducting Measurements of Radon and Radon Decay Products in Multifamily, School, Commercial and Multi-Use Buildings. New York State Department of Health radon guidance and 8 NYCRR 155.5(m). Retrieved 11 September 2026. This article explains published requirements and is not legal advice. Confirm current rules with the relevant agency before acting.