--- title: How Commercial and Multifamily Radon Testing Works canonical: "https://radonmitigationyorkpa.net/radon-guide/commercial-radon-testing-protocol/" pubDate: "2026-10-01T00:00:00.000Z" updatedDate: "2026-10-03T00:18:00.000Z" author: Radon Mitigation York PA description: "How commercial and multifamily radon testing differs from a home test: ANSI/AARST MA-MFLB-2023 test locations, HVAC rules, timing and follow-up." --- # How Commercial and Multifamily Radon Testing Works Commercial radon testing follows the ANSI/AARST MA-MFLB-2023 protocol for multifamily, school, commercial and mixed-use buildings. Compared with a home test, it uses many more test locations, including every occupied room or unit touching the ground and a share of upper floors, and it requires the HVAC to run as it normally does. The results guide any [commercial radon mitigation](/services/commercial-radon-mitigation/) that follows. ## Why large buildings need a different protocol A house is usually one foundation and one HVAC system, so a test or two on the lowest lived-in level tells you a lot. Large buildings are different: - **Many separate spaces.** Each unit, classroom or office can have its own radon level. - **Split foundations.** Additions, footings and grade beams break the slab into sections that behave differently. - **Complex HVAC.** Air handlers, exhaust fans and fresh air intakes change building pressure, which changes how much soil gas comes in. - **Shafts and chases.** Elevators, stairwells and utility chases can move air between floors. A single test in one room cannot represent a whole building. The protocol is built to catch high spots. ## The standard: ANSI/AARST MA-MFLB-2023 In 2023, AARST combined two earlier measurement standards, MAMF for multifamily buildings and MALB for schools and large buildings, into one: ANSI/AARST MA-MFLB-2023. EPA lists it on its [radon standards of practice](https://www.epa.gov/radon/radon-standards-practice) page alongside MAH-2023, the protocol for single-family homes. If you see older reports that reference MAMF or MALB, they were done under the earlier standards. ## Where tests go Under MA-MFLB-2023: - **Ground-contact spaces.** A measurement is made in every dwelling and every occupied nonresidential room with floors or walls in contact with the ground. - **Upper floors.** On each upper floor, measurements go in at least one and not less than 10 percent of occupied dwellings and rooms. - **Placement in the room.** Devices go in the breathing zone, away from drafts, exterior walls, heat sources and high humidity, following the standard's placement rules. For a 40-unit apartment building with 10 ground-floor units, that means testing all 10 ground-floor units plus at least one unit on each floor above. Our article on [radon in apartments and multifamily buildings](/radon-guide/radon-in-apartments/) covers that case in more depth. ## Building conditions during the test Conditions matter as much as locations. ### HVAC running normally Heating and cooling must be set to normal occupied operating conditions, with temperatures between about 65 and 80 degrees F. Systems that bring in outdoor air should run as they would on a normal occupied day. ### Closed-building conditions Windows and exterior doors stay closed, except for normal entry and exit. For tests shorter than 72 hours, closed-building conditions start at least 12 hours before the test. ### Test length The minimum is not less than 46 hours of deployment under closed-building conditions, with at least 48 hours of valid sampling time as the goal. Longer tests give a better average. ### Weekends and schedules Many commercial buildings change HVAC settings at night and on weekends. A test plan has to account for that, so results reflect when people are actually in the building. ## Quality control Large building testing includes quality control measurements, such as duplicate devices in some locations and blank devices, to confirm the results are reliable. The tester documents every location, device and condition. ## Two-step testing and follow-up Testing typically happens in steps: 1. **Initial measurements** across all required locations. 2. **Follow-up measurements** in locations at or above the action level, to confirm results before mitigation decisions. Under the standard, if follow-up testing is not finished within 12 months of the first step, the process starts over. After mitigation, the treated areas are retested. The standard also calls for periodic retesting over time. Mitigated areas should be retested about every two years. All buildings, mitigated or not, should be retested at least every five years and whenever a building is sold. ## Home testing vs. commercial testing | Factor | Single-family home (MAH-2023) | Multifamily and large buildings (MA-MFLB-2023) | |---|---|---| | Test locations | Lowest lived-in level | Every ground-contact occupied room or unit, plus at least 10 percent per upper floor | | HVAC | Normal operation | Normal occupied settings, with attention to schedules and fresh air | | Building size | One foundation, usually | Often several slab sections and additions | | Quality control | Duplicates in some cases | Duplicates and blanks across the project | | Follow-up | Second test or long-term test | Follow-up by location, within set time limits | ## Who can do commercial testing in Pennsylvania Pennsylvania's Radon Certification Act and 25 Pa. Code Chapter 240 require anyone testing radon for others to be certified by PA DEP. That covers apartment buildings, offices, schools and every other building type. You can check certification through the [PA DEP Radon Division](https://www.pa.gov/agencies/dep/programs-and-services/radiation-protection/radon-division). ## York County context York County is in EPA Radon Zone 1, the highest radon potential category. Many local commercial buildings are older brick and stone structures with additions, so different wings can test very differently. Winter often shows the highest results because heating draws more soil gas in, so cold-season testing gives a conservative picture. ## Key takeaways - Commercial and multifamily testing follows ANSI/AARST MA-MFLB-2023, which replaced MAMF and MALB. - Every occupied ground-contact room or unit gets tested, plus at least 10 percent of each upper floor. - HVAC runs at normal occupied settings, under closed-building conditions. - Tests run at least 46 to 48 hours, with quality control devices. - Testers must be PA DEP certified. ## Frequently Asked Questions ### Can I use one long-term test for my office building? Not for the whole building. Each ground-contact room needs its own measurement under the protocol. ### Do vacant units need testing? The protocol targets spaces that are occupied or intended to be occupied, so units waiting for tenants are usually included. ### How long does a commercial test project take? Device deployment is usually a few days. Planning, retrieval, lab analysis and reporting add time. ## Plan your building's radon test We plan and run radon testing for apartments, offices, schools and churches across York. Call [(717) 356-3035](tel:+17173563035) any time for a same-day callback.