Large Building
Radon Testing
ANSI/AARST MA-MFLB-2023
Protocol for Conducting Measurements of Radon and Radon Decay Products in Multifamily, School, Commercial and Mixed-Use Buildings
This standard of practice specifies procedures and minimum requirements when measuring radon concentrations in shared structures, or portions of shared structures used for residential, non-residential or mixed-use purposes to determine if radon mitigation is necessary to protect current and furture occupants.
ProCheck inspections offers Radon Testing for Multifamily, School, Commercial and Mixed-Use Buildings aka Large Buildings. Things have evolved since Colorado’s Radon Bill last year, now tenants in multi-family units, employees in large buildings and buyers in real estate transactions can make owners install a radon mitigation system for their particular unit. Sellers, HOAs and Property Managers should test the entire building for better results. Then you will have disclosures readily available instead of dealing with revolving clients testing on their own. Plus, if necessary, mitigating an entire building is more cost effective than unit by unit. Testing Multiplexes, Office Spaces and Apartment or Townhome Complexes is very different technically than Residential Testing. Call us today for a quote and get it over with!
MFM (Multifamily Measurement) – NRPP Certified professionals who have attended and passed an approved Multifamily Measurement course and practicum session.
What Is Radon?
Radon is a naturally occurring radioactive gas that forms when uranium breaks down in soil and rock. It is completely invisible, odorless, and tasteless, which means the only way to know if it is present in a building is through professional testing.
Radon moves through the ground and can enter buildings through cracks in foundations, gaps around pipes, construction joints, crawl spaces, and other openings. Once inside, the gas can accumulate to dangerous levels, especially in lower floors and poorly ventilated areas.
Long-term exposure to elevated radon levels is a serious health risk. The U.S. Environmental Protection Agency (EPA) identifies radon as the second leading cause of lung cancer, after smoking, and responsible for an estimated 21,000 deaths each year in the United States. More importantly, smoking and high levels of radon increase your chances of lunger cancer x6 times.
Each 10 pCi/l is equivalent to smoking 1 pack of cigarettes, per person, per day.
Because there is no safe level of radon exposure, testing is the only way to protect occupants.
The EPA recommends taking action when radon levels reach 4.0 picocuries per liter (pCi/L) or higher, though mitigation may be recommended even at lower levels depending on building use and occupancy patterns.
Why Radon Testing Matters for Large Buildings
While many people associate radon with single-family homes, it can be found in any type of building, including apartments, condominiums, offices, schools, and commercial properties. In fact, multifamily and large buildings can present unique risks because radon levels often vary significantly between floors, units, and structural sections.
Without comprehensive testing, elevated radon levels in certain areas of a building can go undetected for years, exposing tenants, employees, and visitors to long-term health risks.
For property owners and managers, radon testing is not just about safety — it also helps reduce liability, supports regulatory compliance, and demonstrates a commitment to occupant health. Many organizations now require radon assessments as part of environmental risk management, real estate transactions, and property maintenance programs.
How Radon Testing Works
Professional radon testing follows strict scientific standards to ensure accurate and reliable results. The process begins with a building assessment to determine the number of testing devices required and the appropriate placement locations.
Testing devices are fplaced in the lowest occupied areas of a building, such as ground-floor units, basements, or first-floor office spaces. In large or multifamily properties, multiple devices are deployed simultaneously to capture variations across units and floors.
Short-term radon testing usually takes between 48 hours, while long-term testing is a minimum of 90 days to measure seasonal variations. After the testing period, the devices are collected and analyzed by licensed technicians and/or laboratories.
Once results are processed, a detailed report is provided outlining radon levels, testing locations, and recommendations. When performed according to ANSI/AARST standards, these results can be used for compliance documentation, risk assessments, and mitigation planning.
What Happens If Radon Levels Are High?
If testing identifies elevated radon levels, the next step is mitigation — a process designed to reduce radon concentrations and protect building occupants.
Radon mitigation typically involves installing systems that safely vent radon gas from beneath the building to the outdoors before it can accumulate inside. Mitigation strategies may include sub-slab depressurization systems, ventilation improvements, sealing entry points, or targeted solutions for specific improvements.
In large or multifamily properties, the main difference is that the mitigation company must look at the building as a whole and not just per unit.
When properly designed and installed, radon mitigation systems can reduce radon levels by up to 99%, bringing buildings into safe ranges.
After mitigation, follow-up testing is conducted to confirm effectiveness and ensure ongoing protection. Regular monitoring may also be recommended as part of a long-term indoor air quality management plan.