ResourcesGlossary: fixing
Passive subslab suction
Short answer
Passive subslab suction is a radon vent pipe that runs from under the slab up through the house and out through the roof, with no fan. EPA says it is usually part of the radon-resistant features installed in newly constructed homes.
What passive subslab suction means
EPA describes the layout: a passive radon ventilation system consists of a vertical vent pipe extending up from a sub-slab collection pipe or mat, through the conditioned space of the home, and through the roof. Because the method requires no mechanical devices, it is called passive.
It does less than a system with a fan. EPA puts the typical reduction of passive subslab suction at 30 to 70 percent, and says it is generally not as effective in reducing high radon levels as active subslab suction.
Passive and active, from 6 pCi/L
Each row applies both ends of EPA's typical reduction to a home that would test at 6
| System | EPA's typical reduction | 6 pCi/L becomes, pCi/L | Under 4 pCi/L? |
|---|---|---|---|
| Passive subslab suction | 30 to 70 percent | 4.2 to 1.8 | Only at the high end: 4.2 is still over 4 |
| Active subslab suction | 50 to 99 percent | 3 to 0.06 | At both ends |
What it means for your home
A passive pipe is not a result. EPA says that even if a home is built to be radon-resistant, it should be tested for radon as soon as possible after occupancy.
If the level is still over 4 pCi/L, EPA says the passive system should be activated by having a qualified mitigator install a vent fan.
Where to go next
- Radon fan running cost calculator. Work out what the fan would cost to run if the pipe is made active.
- Passive radon systems: how they work and how to make one active. What the builder installed, whether it is enough, and adding a fan.