If you need vapor intrusion mitigation for a New Jersey project, you will likely choose between two approaches: sub-slab depressurization (SSD) and passive venting. Both work. But they work differently, and one is usually a better fit for your project than the other.
Sub-Slab Depressurization
SSD is an active system. A network of perforated pipes is installed in the stone layer beneath the concrete slab. These pipes connect to a fan mounted on the roof or side of the building. The fan creates negative pressure under the slab, pulling soil gas through the pipes and venting it above the roofline where it disperses safely.
SSD has several advantages. It provides measurable, verifiable protection. A manometer or magnehelic gauge shows the vacuum level at each extraction point. Pressure field extension testing can confirm the system is covering the entire slab. This data is important for NJDEP compliance and gives building owners confidence the system is working.
The downsides are cost and maintenance. SSD costs more upfront because of the fan, electrical work, and monitoring equipment. The fan uses electricity and needs periodic replacement, usually every 5 to 10 years depending on the model. For most commercial projects, though, the reliability is worth the added cost.
Passive Venting
Passive venting uses natural forces instead of a fan. A pipe stack runs from below the slab up through the building and out the roof. Warm air naturally rises through the stack, creating a small negative pressure that draws soil gas out from under the slab. Wind passing over the roof outlet also helps pull air through the system.
Passive venting costs less to install because there is no fan, no electrical connection, and no monitoring equipment. It has no operating costs and nothing to maintain. But it is less reliable than an active system. Performance depends on temperature differences, wind conditions, and building pressure. On calm, warm days when there is little temperature difference between inside and outside, a passive system may move very little air.
Most building codes recognize this limitation. They allow passive venting as a first step but require the piping to be sized so a fan can be added later if post-construction testing shows the passive system is not keeping vapor levels below screening thresholds.
Which One Is Right for Your NJ Project?
For most commercial and industrial projects in New Jersey, SSD is the better choice. NJDEP requirements are strict, and SSD gives you measurable performance data that satisfies regulators. If your site has known contamination or is in an area with a history of industrial use, plan for an active system.
For residential projects or low risk commercial sites where soil testing shows minimal contamination, passive venting may be sufficient. The lower upfront cost makes it attractive, and the ability to add a fan later means you are not locked in if conditions change.
The smart approach is to design for the more demanding system and build the flexibility to start simple. Oversize the pipe runs. Route them to accessible locations. Install the vapor barrier and sub-slab aggregate to SSD standards. That way you can start with passive venting and upgrade to active if needed without tearing up the slab.
EAI-South Does Both
We design and install both SSD and passive venting systems across New Jersey. We can review your site conditions and regulatory requirements and recommend the right approach for your project. Our team understands NJDEP requirements and has completed systems on projects ranging from small residential buildings to large commercial developments. Give us a call to talk through your options.