Radon testing and understanding the radon mitigation system is a detailed process that requires careful planning, professional expertise, and adherence to established guidelines. Radon is a naturally occurring radioactive gas that can accumulate in buildings, posing health risks to occupants. Multi-family buildings present unique challenges due to their size, shared spaces, and varying construction types.
Radon testing is the first step, and must be conducted by a certified professional, such as one accredited by the National Radon Proficiency Program (NRPP) or the National Radon Safety Board (NRSB). They will identify where to place radon detection devices. In multi-family buildings, devices are typically placed in all ground-contact units or areas, as well as at least 10% of units on upper floors. This ensures comprehensive coverage since radon levels can vary significantly between units due to differences in ventilation, construction materials, and proximity to the ground. Testing should also include common areas like lobbies or basements if they are frequently occupied.
The testing process involves using either short-term or long-term radon detection devices. Short-term tests provide results within 48 hours to 90 days and are ideal for quick assessments, such as part of a home inspection for purchasing a condo or the entire building. Long-term tests, which last over 90 days, offer more accurate readings by accounting for seasonal variations in radon levels. The long term testing isn’t appropriate for a home purchase, due to the length of the time the property is under contract. But it is ideal when the condo association agrees to test the building for radon levels in different parts of the building. Devices must be placed according to strict guidelines—away from windows, doors, vents, and exterior walls—to ensure accurate results. Once testing is complete, any unit or area with radon levels exceeding 4.0 picocuries per liter (pCi/L), the EPA’s action threshold, will require mitigation.
If high radon levels are detected, the next step is implementing a radon mitigation system tailored to the building’s design and needs. If this is part of the home inspection for a purchase, the results may impact the buyer’s decision to purchase or walk away. The most common mitigation system for multi-family buildings is Sub-Slab Depressurization (SSD). This system involves drilling small holes into the building’s concrete slab foundation and installing PVC pipes that extend through the building to the roofline. A fan creates negative pressure beneath the slab, drawing radon gas away from the living spaces and safely venting it above the roofline where it dissipates harmlessly.
For buildings with crawl spaces instead of slabs, Sub-Membrane Depressurization (SMD) systems are used. These systems involve covering the crawl space floor with a durable plastic sheet and installing a vent pipe and fan to extract radon gas from beneath the membrane. Other systems like Drain Tile Depressurization (DTD) or Block Wall Depressurization (BWD) may be employed depending on the building’s construction type.
Mitigation systems must comply with local building codes and fire safety regulations. Professional installation ensures proper functionality and minimizes risks associated with incorrect setup. After installation, follow-up testing is conducted to confirm that radon levels have been successfully reduced below 4.0 pCi/L.
Inspecting a multi-family building for radon involves comprehensive testing across multiple units and common areas, followed by implementing an appropriate mitigation system if high levels are detected. The process requires collaboration between property owners, certified professionals, and potentially condominium associations to ensure compliance with safety standards and protect occupants’ health. Properly installed mitigation systems can reduce radon levels by up to 99%, providing peace of mind for residents in multi-family properties.
